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Quantifying the Heat-Related Hazard for Children in Motor Vehicles


Abstract and Figures

Thirty-seven children on average die each year in the United States from vehicle-related hyperthermia. In many cases, the parent or care-giver intentionally left the child unattended in the car, unaware of how quickly temperatures may reach deadly levels. To better quantify how quickly temperatures may increase within a car, maximum rates of temperature change were computed from data collected on 14 clear days in Athens, Georgia. Also, a human thermal exchange model was used in a case study to investigate the influence of different meteorological factors on the heat stress of a child in a hot vehicle. Results indicate that a car may heat up by approximately 4°C in 5 min, 7°C in 10 min, 16°C in 30 min, and 26°C in 60 min. Within the vehicle, the dominant energy transfers toward the child are via longwave radiation and conduction from the hot interior surfaces of the car. Modeling simulations show that sun exposure and high-humidity conditions further increase the heat stress on the child but that ...
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AFFILIATIONS: Gr u n d s t e i n a n d Me e n t e M e y e r —Department of
Geography, University of Georgia , Athens, Georgia; do w d
Depar tment of Geology, University of Georgia, Athens, Georgia
CORRESPONDING AUTHOR : Andrew Grundstein, Department
of Geography, Climatology Research Laboratory, University of
Georgia, Athens, GA 30602
The abstract for t his article can be found in this issue, following the
table of contents.
DOI:10.1175/ 2010B AM S2912.1
In final form 9 April 2010
©2010 American Me teorological S ociet y
A table of maximum rates of temperature change inside motor vehicles should be useful in
educating the public about the dangers of vehicle-related hyperthermia.
The danger of leaving young children unattended
in vehicles has been well documented. There are
no unique codes for identifying vehicle-related
hyperthermia deaths in the International Classifica-
tion of Diseases (ICD) or in any U.S. federal or state
data source (Guard and Gallagher 2005). However,
vehicle-related hyperthermia deaths in children in
the United States have been constructed from news
accounts. Guard and Gallagher (2005) observed an
average of 29 deaths per year during the years 1995–
2002, while a more extensive dataset by Null (2009)
observed an average of 37 deaths per year during the
years 1998–2009. Most cases (54%) involve caregivers
simply forgetting their children; however, more than a
quarter of vehicle-related hyperthermia deaths (27%)
involve children that were intentionally left in the car
(Guard and Gallagher 2005). In some cases, parents
did not want to disturb a sleeping child but were
unaware of how quickly the car could heat up. Such
behavior indicates a clear lack of understanding by
parents and caregivers about the dangers of leaving
children unattended in vehicles.
The interior of a car, along with the particular case
of a child strapped into a child safety seat, represents
a unique environment that may create particularly
dangerous conditions. Multiple studies have investi-
gated how ventilation, shading, and different meteo-
rological conditions may affect maximum cabin tem-
peratures and rates of temperature change (Table 1).
With the car in direct sunlight and no ventilation,
maximum temperatures may reach values exceeding
70°C (Table 1). These stunningly high temperatures
are caused by a greenhouse effect, where the windows
are transparent to solar radiation but opaque to long-
wave radiation. As a result, a positive net radiation
balance occurs that leads to heating. In addition, the
lack of ventilation from closed windows reduces the
transport of energy via convection and further con-
b y an d r e w Gr u n d s t e i n , Jo h n do w d , a n d Ve r n o n Me e n t e M e y e r
tributes to heating. Zumwalt and Petty (1976) note
that exposure to high environmental temperatures
only leads to a large rise in body temperature when
the temperature-regulating mechanisms are not oper-
ating efficiently. In a hot vehicle without ventilation,
physiological mechanisms typically used for cooling,
including longwave radiation and convection, would
be ineffect ive . Furtherm ore, the eff ici ency of e vapor a-
tive cooling would be reduced as evaporated perspira-
tion accumulated in the vehicle.
The meteorological community, along with local
healt h offic ial s and t he me dia , has b een ac tive i n dis-
seminating information about heat-related hazards.
The National Weather Service (NWS), for instance,
will issue “excessive heat warnings” or “heat advi-
sories” depending on the severity of the conditions
(NWS 1994). Many communities worldwide have
adopted synoptic-based heat watch–warning systems
where “heat alerts” and “heat warnings” are issued
(Sheridan and Kalkstein 2004). Layered on top of
these general heat alerts are more specific warnings
by public and private entities about the dangers of
leaving children unattended in motor vehicles. While
most of these warnings include some statements
about how hot a car might get, vehicle temperature
data from many early studies were often obtained
with small datasets and questionable methodologies,
such as placing the temperature sensor directly on
the car seat.
This research will focus on providing infor-
mation that may aid public off icials, child safety
advocates, and the media in better educating the
public about the dangers of leaving children unat-
tended in vehicles. Results from this study may also
be used as part of a public health response to a heat
health warning to emphasize the extreme danger
of vehicle-related hyperthermia in children during
those unusually hot periods. The first portion of the
study determines maximum temperature change at
different time intervals using carefully positioned
high-temporal-resolution temperature sensors. An
extension from previous work involves placing the
results in an easy-to-use table of vehicle temperature
changes that shows conditions that may occur under
the most severe circumstances. In addition, previous
studies have discussed but have not quantified how
the environmental conditions in a car would affect
the energy budget of a child (e.g., Zumwalt and Petty
1976; King et al. 1981). Thus, a human heat balance
model will be used to investigate the energy budget of
Ta b l e 1. Summary of rates of temperature change within passenger vehicles from different studies. Values
were estimated from figures and tables presented in the various studies and selected to represent cases
when the car had minimum ventilation and was in direct sunlight. Max is the maximum temperature
reached while the car was parked. All values are rounded to the nearest degree Celsius. The asterisk
means that day temperatures reached 89°C , and the car was parked for 12 h.
min Max
Instrument type
and location
(h) Location and dates
Gibbs et al. (1995) 7 16 24 27 60 Electronic; placed
on front seat 1.5 New Orleans, LA ;
27 Jul 1995; 1430–1600 LT
Grundstein et al. (2009) 76 Electronic; 15 cm
below roof center 6Athens, GA;
1 Apr–31 Aug 2007
King et al. (1981) 19 21 25 25 66 Electronic; 15 cm
below roof center 2
Brisbane, Queensland,
Australia; summer 1978 and
1979; 1100–1300 LT
Mart y et al. (2001) 89 Electronic 12*
Zurich and Chur,
Jan 1995– Mar 2000
McLaren et al. (2005) 4–10 7–13 17–18 22–23 47 Electronic; 38 cm
above rear seat 1Freemont, CA ; 16 days;
15 May–8 Aug 2002
Roberts and Roberts
(1976) 15 45
Liquid in glass;
15 cm above front
seat cushion
0.75 Baltimore, MD;
Sep 1975; afternoon
Surpure (1982) 78
Liquid in glass;
suspended from
driver’s seat
Oklahoma City, OK;
first week, Jul 1980;
080 0–1600 LT
Zumwalt and Petty
(1976) 58 Liquid in glass;
back seat 5Dallas, TX; Jun– Oct 1975;
1200–1700 LT
1184 SEPTEMBER 2010
a child in a hot car and the influence of variations in
humidity and sun exposure on levels of heat stress.
DATA AND METHODS. Ai r temperatu res
within a vehicle were measured on 58 days—from
April through 31 August 2007—in Athens, Georgia
(33.95°N, 83.32°W). Measurements were taken within
a metallic gray 2005 Honda Civic with gray cloth
seats. Approximately 67% of vehicle-related hyper-
thermia deaths in children occur in cars as opposed
to larger vehicles, such as minivans or SUVs; there-
fore, a car provides a representative vehicle for the
study (Guard and Gallagher 2005). In addition, tem-
peratures increase more rapidly in smaller vehicles
(Surpure 1982), thus providing better estimates for
“worst case” scenarios. The car was parked in an open
asphalt-covered lot with direct exposure to sunlight.
Additionally, the windows were closed during data
collection to limit ventilation and maximize heating
within the vehicle.
The vehicle temperature data were collected by an
Onset Computer Corporation HOBO temperature
sensor (H008-003-002; resolution = 0.4°C, accuracy
= ±0.7°C) that recorded temperatures every 5 min.
The sensor was attached to a string and suspended
approximately 15 cm from the ceiling to avoid direct
exposure to sunlight and to be sufficiently far from
surfaces to accu rately measure air temperature.
Ambient outdoor air temperature, dewpoint tempera-
ture, and solar radiation
data at a 5-min resolution
were obtained from an ad-
jacent weather station op-
erated by the Department
of Geography Climatology
Research Laboratory (CRL),
located on the roof of the
bu i lding approx i mat ely
12 m higher in elevation
tha n t he car and 125 m
from the parking lot. Solar
radiation was measu red
with a Davis 6450 silicon
phot odiod e s enso r, and
temperature and humid-
it y were measu red with
a shielded and aspi rated
Davis 6382 temperat ure
and humidity sensor. Cloud
cover data at hourly resolu-
tion were obtained from a
NWS Automated Surface
Observing Station (ASOS)
located approximately 5 km away at Athens–Ben
Epps Airport.
For each day with vehicle temperature data, the
maximum 5-, 10-, 30-, and 60-min temperature
changes were computed. The focus of the study is on
the most severe possible conditions with the greatest
temperature changes. Thus, maximum temperature
changes were examined only for clear days. In total,
14 days—ranging from 12 April to 24 July—were
examined (Table 2). This period encompasses dates
near the spring equinox and the summer solstice, pro-
viding for a variety of solar angles and solar radiation
values. Maximum rates of temperature change were
assessed from 1100 to 1300 EDT to capture the pe-
riod in the vicinity of solar noon (around 1300 EDT)
when solar heating would be most intense. Graphs of
car temperatures (Figs. 1 and 2) show that the rates
of temperature change are reduced approaching
1300 EDT, as the hot car emitted greater amounts of
longwave radiation relative to incoming solar radia-
tion, thereby reducing net radiation.
The second portion of the study examines the en-
ergy budget of a child in a hot car using a human ther-
mal exchange model called the man–environment
heat exchange model (MENEX). It has been employed
in several experimental studies of the human thermal
budget (e.g., Katavoutas et al. 2009; Tuller 1997) and
is capable of computing the various energy budget
components, including absorbed solar radiation,
Ta b l e 2. Interior vehicle air temperature change by time inter val
and average solar radiation (1100–1300 EDT) for study days in 2007.
Temperature is in degrees Celsius, and the solar radiation is in watts per
square meter.
Month Day 5 min 10 min 30 min 60 min Solar
413 1.7 3.3 9.6 17.4 794
416 2.0 3.3 9. 3 16.8 8 21
417 2.5 4.7 12.3 21.0 850
425 3.4 6.4 12 .9 20.4 810
430 3.0 5.5 14.7 24.0 840
501 3.6 6.8 14.1 21.0 829
521 3.0 5.6 15. 6 25.8 860
522 2.1 3.8 10.8 18.6 794
530 2.6 5.1 13 . 5 24.0 790
618 1.8 3.2 8.7 15.0 776
621 3.5 5.8 13.8 25.8 884
622 2.8 5.0 13. 5 24.0 878
712 2.5 4.5 12 .6 22.2 850
724 3.0 5.9 15.6 24.6 813
net longwave radiation, turbulent fluxes of sensible
and latent heat, as well as metabolic heat production
and heat loss through respiration (Błażejczyk 1994).
Further, MENEX accounts for physiological factors
such as skin temperature, skin wetness, and clothing
albedo and insulation. The human heat balance equa-
tion is defined as
S = M + Q + H + LE + C + Res, (1)
where S is the net heat storage or change in body
heat content; M is metabolic heat production; Q is
the radiation balance of the person; H and LE are
convective transfers of energy via sensible and latent
heat, respectively; C is conduction; and Res is the heat
loss by respiration. Positive (negative) fluxes indicate
a gain (loss) in net heat storage. Changes in the body
heat content will be used to quantify the heat stress on
the child. The degree to which changes in body heat
content relate to particular health outcomes such as
heat stroke or death, however, is not
well established and may vary with
the age and health of the child.
Model simulations were per-
formed of a child seated inside the
car as well as one outside the car
to serve as a reference. The human
thermal exchange model was modi-
fied slightly for the simulations of a
child within the car. First, longwave
radiation emitted by the interior of
the vehicle was determined using the
average interior surface temperature
and the Stefan–Boltzmann equation
with an emissivity of 0.97. Second, a
conduction term was computed to
account for the fact that a child would be strapped in
a child safety seat as follows:
C = K(TcarTskin)A, (2)
where K is the heat transfer coeff icient t hrough
clothing as computed by MENEX, Tcar Tskin is the
temperature gradient between the child’s skin Tskin
and safety seat Tcar, and A is a constant that accounts
for the portion of the child’s body that is in contact
with the seat. Here, the simulation is performed for
a 2-yr-old toddler sitting in a forward-facing child
safety seat. A contact value of 0.24 is used, which
represents a child’s torso, legs, and head in contact
with the seat (Raja and Nicol 1997). The degree of
contact, however, may vary somewhat with the par-
ticular child safety seat used. For instance, the degree
of contact may be higher in an infant safety seat that
is designed to cradle the child. Nevertheless, the re-
sults should approximately represent conditions for
children 3 yr old or younger who are placed in child
safety seats.
Several input values were adjusted to account for
the physiology of the child and the climate conditions
within the car (Table 4). The physiological charac-
teristics of an average 2-yr-old toddler were used in
modeling. The metabolic rate of the child was esti-
ma ted at 61 W m−2, which is consistent with the caloric
needs of 700 kcal day−1 (Durnin 1981). Ambient air
temperatures during the study period were generally
high; therefore, it is assumed that the child is dressed
in summer attire with clothing insulation of 0.6 clo1
(Błażejczyk 1994). Also, the child is assumed to be
Fi g . 2. Time series of interior vehicle air temperatures,
ambient outdoor air temperatures, and solar radiation
from 0900 to 1700 on 22 Jun 2007.
1 ANSI/ASHRAE (1992) defines a “clo” as a unit to express
the thermal insulation provided by garments and clothing
ensembles, where 1 clo = 0.155 m2*C / W.
Fi g . 1 . Interior vehicle air temperatures between 1100 and 1300 EDT
on 14 different clear days.
1186 SEPTEMBER 2010
unacclimatized to hot conditions with skin that is
initially 33°C and dry (Fanger 1972; Hoppe 1998).
Physiological changes are simulated by increasing
the sk in t empe rat ure and wetn ess . Mod eled s kin tem-
peratures were not used, as Katavoutas et al. (2009)
found the empirical equation used in MENEX may
not be appropriate to use for unacclimatized people.
Rather, skin temperatures were varied from 33°C to
a maximum of 37°C in 20 min based on observations
from Fiala et al. (2001), where unacclimatized sub-
jects were exposed to high temperatures. All model
simulations used the same skin temperatures, so that
the influence of different environmental conditions
could be isolated. Wetness is computed as a function
of skin temperature, reaching complete wetness at
temperatures >36.5°C (Błażejczyk 1994). Wind speed
in the car without ventilation (i.e., windows rolled
up) is minimal. A nominal value of 0.1 m s−1 is used,
which is similar to values used in studies of indoor
climates (Hoppe 1998).
Model simulations were performed for 22 June
2007 from 1300 to 1400 EDT using data collected
from the study vehicle and the nearby CRL weather
station. This was a clear day, falling near the summer
solstice and providing suitable conditions for a case
study of a worst-case scenario. Input solar radiation
and humidit y data were obtained from the CRL
weather station. Initial humidity levels in the vehicle
were assumed to be similar to outside values, as air
was entrained in the vehicle while placing the child in
the car. Over time, evaporated perspiration from the
child would increase humidity within the vehicle. All
perspiration was assumed to evaporate, and dewpoint
temperatures were iteratively increased each time
step. The windows of the vehicle attenuate some of
the incoming solar radiation. Measurements of solar
radiation taken inside and outside the car indicate
that values within the vehicle were reduced by ap-
proximately 50%. Thus, only half of the measured
solar radiation was input into the model. The interior
surface temperatures of the car were obtained using
an Omega OS530HR handheld infrared thermom-
eter. Measurements were taken of the seats, floor,
ceiling, and windows and averaged to provide a rep-
resentative interior surface temperature. The average
interior surface temperature was used in computing
longwave radiation emissions from the car, and the
seat temperature was used in calculating the conduc-
tion term.
RE S ULTS . Maximum rates of temperature change.
The 14 days utilized in this study provide a repre-
sentative sample for assessing ideal conditions for
maximum heating (Table 2). The sample data are
distributed over the entire study period, with days in
each month from April through July. Overall, there
were 36 days with clear skies and 30 of those days
with solar radiation data. The average solar radiation
during peak heating periods (e.g., 1100–1300 EDT)
for those 30 days was 824 W m−2 , with a range from
758 to 884 W m−2. The data used for this study had
average solar radiation that was slightly greater at
828 W m−2 and a range from 776 to 884 W m−2. The
sample dataset includes the two days with the greatest
average solar radiation and three other days among
the top 10 in solar radiation.
There were different initial ambient air tempera-
tures and rates of temperature change for the 14 peak
heating periods studied (Fig. 1). Initial ambient air
temperatures at 1100 EDT ranged from 15° to 34°C,
with temperatures reaching 43°–62°C by 1300 EDT.
Temperature changes were computed for 5-, 10-, 30-,
and 60-min periods (Table 2). The average (maxi-
mum) temperature change over each time interval
is 2.7°C (3.6°C) for 5 min, 4.9°C (6.8°C) for 10 min,
12.6°C (15.6°C) for 30 min, and 21.5°C (25.8°C) for
60 min. The comparatively lower rates of temperature
change for cloudy days is indicated by looking at
values on two days (4 May and 2 July) with complete
cloud cover. Average temperature changes are 1.7°C
for 5 min, 3.0°C for 10 min, 7.6°C for 30 min, and
8.9°C for 60 min.
At longer time intervals, these results are consis-
tent with other studies that observed hourly tempera-
ture increases ranging from 22° to 27°C (McLaren
et al. 2005; Gibbs et al. 1995; King et al. 1981). There
are some differences with other studies at shorter
intervals that are likely related to the positioning of
the sensors. Large rates of temperature change may
have been related to the exposure of the sensor to
direct sunlight (King et al. 1981) or the location of
the sensor on the car seat (Gibbs et al. 1995), which
would be influenced by the seat temperature and not
be representative of vehicle air temperatures. In all
cases, the maximum temperature changes occurred
around noon. This timing is tied to the radiation
balance of the vehicle and can be illustrated using
measurements of incoming solar radiation and ve-
hicle air temperatures for 22 June 2007 (Fig. 2). The
cabin and ambient air temperatures are relatively
similar early in the day but diverge rapidly between
1130 and 1300 EDT. Between 1100 and 1300 EDT, the
solar angles are high (61°–79°C, respectively), leading
to intense solar heating of the car seats, which in turn
warms the overlying air. Any increase in temperature
of the car, however, will lead to increases in longwave
emissions to the fourth power, as indicated by the
Stefan–Boltzmann law. Thus, the enormous rise in
car temperature during this time increases longwave
emissions relative to incoming solar radiation and
slows the subsequent rate of heating.
A table of maximum vehicle temperature changes. A
table of maximum passenger compartment tem-
perature changes was developed to aid in advising
the public about the dangers of leaving children un-
attended in cars (Table 3). The table considers initial
ambient air temperature when the car is parked, and
the temperature changes for 5-, 10-, 30-, and 60-min
intervals. The table is designed to show the maximum
possible changes in temperature over each interval by
using the greatest observed temperature changes from
Table 2. Of course, factors such as whether the car is
in direct sunlight, the time of day (i.e., different solar
angles and solar radiation), the amount of cloudiness,
an d ventil ation (i.e., win dows rolle d dow n) wil l inf lu-
ence the actual amount of temperature change.
Table 3 shows that the thermal hazard is a func-
tion of both the initial ambient air temperature and
the time interval over which the heating occurs. One
way to characterize the meaning of these tempera-
tures in terms of a health hazard is to place them in
the context of heat health warnings
provided by the National Weather
Service (NWS 1994). For example, a
heat advisory is issued by the NWS
when the heat index is 41°–4C
for less than 3 h. An excessive heat
warning is issued when the heat
index is ≥41°C for more than 3 h
or exceeds 46°C for any period of
time. Thus, one could say that if the
outside air temperature is 34°C, then
the vehicle could reach the level of a
heat advisory within 10 min and an
excessive heat warning within 30
min. Of course, the temperatures
listed in the table only provide an
indicator of the level of danger. One
must consider the age and health
of the child when assessing danger
as well as the fact that children in
general are particularly susceptible
to heat-related illnesses (Hoffman
2001). Children’s smal l size gives
them a high surface-area-to-mass
ratio that a llows them to absorb
more energy from the environment
than an adult, and their ability to
cool through perspiration is less efficient (Hoffman
2001). In addition, young children are not able to
adjust their behavior in response to the heat, such as
removing clothing or exiting the car (McLaren et al.
2005; Hoffman 2001)
Modeling the energy budget of a child in a hot car. A
human heat balance model was used to examine the
influence of humidity and full sun exposure on the
heat stress of a child in a hot vehicle. The modeling
study was performed using data collected from a 2005
Honda Civic that was parked for approximately 4 h.
During the study period from 1300 to 1400 EDT, the
sky was clear; outdoor air and dewpoint temperatures
averaged 33° and 11°C, respectively; and solar radia-
tion was 954 W m−2 . Outside wind speeds, adjusted
from the roof to 1.5 m using a logarithmic wind
profile, were low at approximately 1 m s−1. The air
temperature within the vehicle averaged 65°C, and
the average temperature of interior surfaces includ-
ing the ceiling, floor, seats, and windows was 69°C.
Model simulations were conducted in 5-min time
steps during the course of the hour.
Fou r si mulat ions were pe rformed for a ch ild wit h-
in the car, including a default simulation and simula-
tions representing conditions with high humidity, low
Ta b l e 3. Maximum interior vehicle air temperature reached for
different time intervals. The values are rounded to the nearest
degree, so that the car heats by 4°C in 5 min, 7°C in 10 min, 16°C
in 15 min, and 26°C in 60 min.
Initial ambient air temperature (°C)
50 54 57 66 76
48 52 55 64 74
46 50 53 62 72
44 48 51 60 70
42 46 49 58 68
40 44 47 56 66
38 42 45 54 64
36 40 43 52 62
34 38 41 50 60
32 36 39 48 58
30 34 37 46 56
28 32 35 44 54
26 30 33 42 52
24 28 31 40 50
22 26 29 38 48
20 24 27 36 46
5 min 10 min 30 min 60 min
Time interval
1188 SEPTEMBER 2010
humidity, and shade. Dewpoint temperatures where
varied by ±10°C about the mean observed dewpoint
temperature of 11°C to simulate high (21°C) and low
(1°C) humidity conditions. In the shade scenario,
the child is not exposed to direct beam radiation but
does receive some diffuse solar radiation, assumed
to be 30% of global solar radiation (Rosenberg et al.
1983). For comparison, a model simulation was also
performed for t he same day and times of a child
standing outside the car. Output from the model
included absorbed solar, net longwave, latent heat,
sensible heat, conduction, metabolic heat production,
respiratory heat losses, and net heat storage.
The average change in body heat content of the
child in the hot vehicle during the 1-h period was
250 W m−2 (Table 4). This is more than 3 times the
net storage gain for a child standing outside of the
car. The energy transfer mechanisms directed toward
the child were very different inside and outside the
vehicle. Within the vehicle, net longwave accounted
for 44%, conduction for 28%, sensible heat for 16%,
and solar for 12% of the exogenous energy transfers to
the child. Thus, the dominant energy transfers were
via conduction and longwave radiation. Outside of
the car, most of the energy transfers to the child were
from solar radiation, with approximately 89% from
solar radiation, 10% from net longwave radiation, and
1% from sensible heat.
The great difference in both the magnitude and
distribution of energy f luxes may be explained by
the unique environment of the interior of the hot
vehicle. The extremely high surface temperatures
in the vehicle direct t he vast majority of radiant
energy in the form of longwave radiation toward
the child as well as transferring large amounts of
energy v ia conduct ion t hroug h the c hild s afety seat.
The relatively small contribution from absorbed
solar radiation occurs because the wi ndows attenu-
ate some of the insolation, and the projected area
that strikes the body is small during periods with
high solar angles. The strong temperature gradient
between the air and child’s skin results in transfers
of sensible heat toward the child; however, the flux
is only 43 W m−2 because of the lack of turbulence.
Evaporative cooling from latent heat transfers away
from the child averages −80 W m−2 . The small value
is related to the low turbulence and the negative
feedback of increased humidity levels in the vehicle
from evaporated perspiration. Indeed, moisture
from the child increased the relative humidity (RH)
from 6% to 19% during the hour. The results support
the observations of Zumwalt and Petty (1976) that
mechanisms that are generally available for cooling
are either reduced (evaporation of perspiration) or
actually lead to heat gains for the child (longwave
radiation and sensible heat).
Ta b l e 4. Average input and output values for human heat balance model simulations of a child in a hot
car for 22 Jun 2007 from 1300 to 1400 EDT. All values except for clothing insulation and wind speed are
rounded to the nearest whole number.
Variable Outside
Biophysical inputs Skin temperature (°C) 33 36 36 36 36
Clothing insulation (clo) 0.6 0.6 0.6 0.6 0.6
Meteorological conditions Air temperature ( °C) 33 65 65 65 65
Average cabin surface
temperature (°C) 69 69 69 69
Initial dewpoint ( °C) 11 11 21 −1 11
Initial/final RH (%) 26/24 6 /19 11 / 2 0 3 /19 6/19
Wind speed (m s−1)1.0 0 .1 0.1 0.1 0.1
Energy fluxes Absorbed solar (W m−2)62 32 32 32 10
Net longwave (W m−2 ) 7 119 119 119 11 9
Sensible heat (W m−2) 1 43 43 43 43
Latent heat (W m−2)−53 −80 −60 −90 −80
Conduction (W m−2 ) 0 77 77 77 77
Metabolism (W m−2)61 61 61 61 61
Respiration (W m−2 )−5 −2 −2 −3 −2
Net heat storage (W m−2)78 250 270 239 228
Simulations were performed to examine how
shading and variations in humidity would affect the
change in the body heat content of the child. The first
set of simulations varied the initial dewpoint from −1°
to 21°C. As one would expect, the drier (more humid)
conditions are associated with greater (less) evapo-
ration. The high-humidity scenario resulted in 8%
gr eater net hea t storag e as a res ult of reduce d ev apor a-
tive cooling. In contrast, the greater latent heat fluxes
away from the child in the low-humidity simulation
reduced net heat storage by about 4% compared
with the default simulation. The relative differences
among the different scenarios were small because of a
negative feedback of evaporated perspiration; that is,
increased perspiration will lead to greater humidity
within the car, which will reduce humidity gradients
and subsequent evaporation rates. This feedback ex-
plains how relative humidity for both the high- and
low-humidity scenarios began at different values but
converged near 20%. The second set of simulations
involved the child being shaded from direct sunlight.
This reduces absorbed energy by 22 W m−2 and the
total heat storage by approximately 9%.
That case study represents a particularly harsh
scenario. Some children are “forgotten” and left in
the vehicle all day, while others are placed in hot
cars in the middle of the day, in some cases with a
broken air conditioner blowing hot air, and have died
wit hin 15 mi n (Associated Press, 24 August 2005 and
9 August 2006). Thus, the energy balance of the child
and the rate at which the child would suffer a heat-
related illness will vary depending on the particular
conditions. Air and surface temperatures of the car,
for example, will differ depending on how long the
car has been parked, whether it is in direct sunlight,
and the degree of ventilation. Also, absorbed solar
radiation may actually increase earlier or later in the
day as lower sun angles lead to larger surface areas
on the body that are exposed to sunlight.
CONCLUSIONS. More than 2,500 children die
each year from unintentional injuries in the United
States (Borse et al. 2008). While the number of chil-
dren who die from vehicle-related hyperthermia is
only a small percentage of this total, it is a hazard
that is so easily preventable. Children should never
be left unattended in vehicles, regardless of ambient
air temperatures, because of risks such as abduction
or injury to the child from incidents such as being
asphyxiated from entrapment by vehicle windows
(NHTSA 2009). However, there is a clear pattern—
both seasonally and by temperature threshold—to
vehicle-related hyperthermia deaths that suggests
targeted “reminders” may be helpful as a warning
strategy. Approximately 75% of deaths occur during
the summer months (Guard and Gallagher 2005) and
data from 231 vehicle-related hyperthermia deaths
during the 2003–08 period show that more than 70%
occurred on days with maximum outdoor tempera-
tures ≥31°C (Null 2009). In direct sunlight and during
the course of an hour, temperatures within a car could
exceed 57°C on such days. Modeling results show that
the dominant transfers of energy toward the child
(longwave radiation and conduction) are driven by
temperature; therefore, passenger compartment air
temperatures serve as a good indicator of the heat-
related hazard. High humidity and exposure to direct
solar radiation will also increase the net heat storage
of a child; however, the inf luence of humidity varia-
tions is limited because of a negative feedback.
Unfortu nately, many people are u naware of
the dangers of leaving a child unattended in a car.
Thus, education may be an important component
in reducing vehicle-related hyperthermia deaths.
Sheridan (2007) documented that heat health warn-
ings are helpful in raising awareness of the dangers
of heat-related illness. An easy-to-use table of vehicle
temperatures changes, as presented here, may help
public off icials and the media communicate with
the public about the hazard of vehicle-related hyper-
thermia in children. Temperature thresholds used
by the National Weather Service for their heat health
warnings may be used to place the temperatures in
the context of healt h hazards. Importantly, these
thresholds should only be used to emphasize how
quickly temperatures in a car can reach hazardous
levels and therefore as a warning to never leave a child
unattended in a vehicle. We hope this characteriza-
tion linking temperatures with an explicit warning
about health dangers to children will modify the
behavior of caregivers and result in fewer tragedies.
Preventing injuries to children from vehicle-related
hyperthermia will ultimately require a multifaceted
approach including education, regulation, engineer-
ing, and legislation (Guard and Gallagher 2005).
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childhood injury report: Patterns of unintentional
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fatalities in the United States, 1995-2002. Inj. Prev.,
11, 33–37.
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... Although many studies have monitored the micro-environment dynamics of the heating of vehicle interiors, few studies have addressed the impact of interior heat loads in terms of children's overall heat balance, physiology, and radiation loads. Such studies assess children's energy balance and core temperature [26][27][28], and have examined death caused by asphyxia or heat stroke in an enclosed space [29]. ...
... The solar canopy structure effectively blocks approximately 95% of the direct incoming solar radiation. The K in hitting the window was multiplied by a window attenuation factor of 0.5 based on invehicle data from Grundstein et al. [26] Given the low likelihood of the child being directly in the sun, we do not account for direct incoming K in as part of the radiation imposed on the child. However, the amount of K in entering the car and being reflected at the child (K r ) remains an important component. ...
... Since 24% of a child's body is estimated to be touching the car seat, conductive heat gain (K) in W m ¡2 was calculated as [26]: ...
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Pediatric deaths due to children being left in hot cars remain a significant yet preventable public health concern. The current study aims to demonstrate the influence of vehicle type, time of day, and solar exposure (sun or shade) on the energy balance and core temperature (Tc) of a hypothetical two-year old boy left in a vehicle on a hot day. Cabin temperatures and relative humidity were collected within six enclosed vehicles under sun or full shade in Tempe, Arizona. These variables and radiation estimates were used to estimate the human energy balance and final Tc across 76 measurement cycles lasting approximately 60minutes. Interior temperatures averaged 39.5°C and 47.6°C in the shade and sun, respectively, at steady-state. Based on the specific heat of a human body, the average Tc after 60 minutes in shaded or sun-exposed vehicles was estimated to reach 38.2±0.29°C and 39.1±0.41°C, respectively, with a significantly higher final Tc in sun-exposed vehicles across all days and in the shaded minivan. Extrapolation to 2 hours is estimated to result in heat injury in the sun. Results demonstrate the influence of radiation on a child's thermal balance in a hot and dry environment. In real-world situations, it is critical to acknowledge variability between children, the starting car environment, and climate (e.g., humid versus dry), and that a child left in any vehicle car can experience potentially lethal core temperatures if forgotten, as shown by vehicular heat stroke statistics. Findings may improve public messaging and reinforce the need for policy action and technological adoption to prevent injury and death.
... Nevertheless, the most prominent issue is the children and infant 5 trapped inside the hot car cabin can be exposed to the risk of hyperthermia or heatstroke. Grundstein et al. 6 computed a simple model to relate heat transfer and the heat coefficient between the children and the air temperature in an enclosed car compartment and concluded that temperature was an important factor to pose a threat to the children left unattended. A dynamic model was also computed by Horak et al. 7 to find out the relationship between air temperature, wind velocity and global radiation which relates to the time required for causing a heat stroke. ...
... Grundstein et al. 6 tabulated some previous findings of rates of temperature variation in an enclosed car and noted that in a car with no ventilation, the peak temperature could easily reach 70°C and higher. The research was then carried out by focusing on the maximum temperature for the worst condition that could happen in a car cabin. ...
Thermal accumulation in a car cabin under direct exposure to sunlight can be extremely critical due to the risk of heatstroke especially to children who are left unattended in the car. There are very limited studies in the literature to understand the thermal behaviour of a car that is parked in an open car park space and the findings are mostly inconsistent among researchers. In this paper, the studies of thermal accumulation in an enclosed vehicle by experimental and computational fluid dynamics simulation approaches were carried out. An effective and economical method to reduce the heat accumulation was proposed. Different test conditions such as fully enclosed, fully enclosed with sunshade on front windshield and different combinations of window gap sizes were experimented and presented. Eight points of measurement were recorded at different locations in the car cabin and the results were used as the boundary conditions for the three-dimensional computational fluid dynamics simulation. The computational fluid dynamics software used was ANSYS FLUENT 16.0. The results showed that the application of sunshade helped to reduce thermal accumulation at car cabin by 11.5%. The optimum combination of windows gap size was found to be with 4-cm gap on all four windows which contributed to a 21.1% reduction in car cabin temperature. The results obtained from the simulations were comparable and in agreement with the experimental tests.
... Perodua Myvi, a national car model, was selected as the test vehicle as it is one of the highest selling cars in Malaysia. Apart from that, this model was chosen due to its smaller size as the temperature increment inside the car can be observed more rapidly (Grundstein et al., 2010). To avoid any potential effects of body color although it has been proven that it has negligible effect (Manning and Ewing, 2009) and also type of tint used to the resulting temperature, only vehicles with dark color and equipped with tint film in the range of RM200 to RM400 were chosen. ...
... All the test vehicles were parked close to each other as in typical open car park setting. In addition, all windows were shut to limit the ventilation and maximize the vehicle heating (Grundstein et al., 2010;Al-Kayiem et al., 2010). Figure 2 shows the difference in vehicle cabin temperatures for every minute. ...
... The self-ignition temperatures obtained, values between 389 and 446 °C, are very high to be reached in closed rooms, even subjected to direct sunlight, such as cars, containers, etc., unless whether they are ovens. The example of the maximum temperatures recorded, between 59 and 78 °C, in closed vehicles [24][25] is very edifying. The temperature reached in containers because of the sun will depend on the time of year, whether the container is made of steel or prefabricated, whether isolated or in group of containers, etc. ...
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Hydro-alcoholic gel using and storage poses a higher risk of fires or injuries due to ignition or self-ignition. The self-ignition temperatures of hydro-alcoholic gels, sold in supermarkets in Abidjan (Cote d'Ivoire), were determined using the isothermal oven procedure and analyzed described in standard DIN 51794. The results obtained throw light on the optimum volume of hydro-alcoholic gel and aluminium tanks to use to self-ignite. The self-ignition temperatures of hydro-alcoholic gel obtained, range from 389 to 446°C with an average of 417.45 ± 14.40°C. This result showed a good agreement with the safety data sheets for some hydro-alcoholic gels. In addition, we found that the temperatures recorded are very high to be reached in closed rooms, even subjected to direct sunlight, such as cars, containers, etc. Therefore, the hydro-alcoholics gels self-ignition temperatures cannot be achieved by use or storage in rooms subject to ambient temperature, except in the case of heat energy source application such as a pilot flame.
... In the summer, the cars are exposed to strong sun when vehicle is parked in the open air without the sunscreen, the heat generated inside the car could increase the interior temperature up to 80ºC [1]. The thermal accumulation inside a car will cause an uncomfortable sensation, animals and children were severely injured by being left unattended in closed and locked parked cars [2]. High temperature will accelerate interior aging and damage to materials such as tape cassettes and plastic components of the car. ...
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In the summer, the cars are exposed to strong sun when it is parked outdoor without the sunscreen, it has had accelerated the auto parts, interior aging and damage. In order to prevent that exposure, the solutions showed such as car awning, car sunshade and car sunscreen etc…, the above devices showed low effectivity for car sun protection. This paper will study effects of cooling system for outdoor sparking car using solar panels cover. A new covering car with multi-layers structure attaching flexible solar panels were designed to increase effectively sun protection, the nitrile rubber foam divided the light and heat radiation of the sun, the flexible solar panel converted solar energy into electric energy and supplied for the air conditioner to regulate inside car temperature. The results showed that, at nitrile rubber foam layer thickness of 4mm, the car maximum temperature of 41.5°C was observed for solar panel-awning-nitrile rubber cover which is much lower than it is exposed directly by sun radiation and commercial cover. The six solar panels (100W) were adapted on car cover, the solar electric energy supplied enough for a mini air conditioner of 340W. Performance of cooling system using solar panels was also investigated and it showed that the temperature inside car could be down to 24°C.
... To further complicate matters, a large portion of the current research literature focuses on questions driven by the physical sciences when in reality this issue lies at the intersection of public health, injury prevention and the atmospheric sciences. For example, the major topics of discussion surrounding this issue include understanding the microclimate conditions in a vehicle [2][3][4][5][6][7][8][9][10][11] and examining the characteristics of past incidents. [12][13][14][15] The next step in the process of understanding these tragic incidents, then, is to connect this scientific information to improve and promote more effective public health messaging. ...
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Introduction On average, in the USA, 37 young children die every year due to vehicular heatstroke. Additionally, over half of these incidents occur when a parent/caregiver forgets a child in a vehicle. While various governmental and child safety advocacy groups have worked to raise awareness about these tragedies, rigorous studies have yet to be conducted that examine the current understanding and effectiveness of this public health messaging. Methods This study will employ a mental models approach in order to identify differences that exist between experts’ and parents’/caregivers’ knowledge and beliefs surrounding the topic of children forgotten in hot cars. We interviewed a diverse set of 25 parents/caregivers and seven experts in order to construct and explore these mental models. Results A comparative analysis was conducted, and three key differences were observed between these mental models. Unlike the experts, the parents/caregivers in the study emphasised perceived lifestyle factors (eg, low-income parent) as important elements in increasing an individual's likelihood of forgetting a child in a car. Importantly, the parents/caregivers primarily obtained information from news reports, while experts believed public health campaigns would reach more parents/caregivers. Lastly, while experts stressed that this tragedy could happen to anyone, most parents/caregivers failed to acknowledge that they could forget their own child in a car. Conclusions To confront this denial, future public health messaging must strive to engage and reach all parents/caregivers. This can be accomplished using a multifaceted messaging strategy that includes personalising core messaging, providing additional resources to media outlets and building rapport between key partners.
The motivation of this work is to respond to high cabin temperatures within a parked/stationary vehicle which may cause discomfort and lead to vehicular heatstroke. The system also intends to ensure sufficient limits of oxygen within the vehicle cabin to prevent asphyxiation to the cabin occupants. The rise in global temperature is affecting the quality of air and comfort of occupants inside a parked car. There have been several cases reported of pets and children being left unattended or unsupervised in a parked car for a long period of time which have led to their deaths due to asphyxiation. The use of cost-effective materials like high density plastics for interior cabin trim have also been proven to contribute to cancer because of the emission of benzene a carcinogen by these plastics when exposed to extreme temperatures for long periods of time. This paper proposes a system where an oxygen sensor is used to measure oxygen levels within the cabin and an arrangement to lower the windows when a low level of oxygen is detected. The system also includes a temperature sensor with a suction and blower fan arrangement where the suction fan pulls the hot air out and the blower fan pushes fresh air in. This air flow will ensure air circulation in a parked car and prevent the stagnation of hot air within the vehicle cabin. It was also a crucial factor that this system should not interfere or hinder with any other workings of the car. This system will be powered by a compact solar system.
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This represents one of several sections of "A Bibliography Related to Crime Scene Interpretation with Emphases in Geotaphonomic and Forensic Archaeological Field Techniques, Nineteenth Edition" (The complete bibliography is also included at This is the most recent edition of a bibliography containing resources for multiple areas of crime scene, and particularly outdoor crime scene, investigations. It replaces the prior edition and contains approximately 10,000 additional citations. As an ongoing project, additional references, as encountered, will be added to future editions. The citations in this section of the bibliography address the effects of temperature ante-, peri-, and post-mortem. Hypo- and Hyperthermic reactions preceding death may account for the context of artifacts within a scene. Most crime scene investigators are familiar with the phenomenon of paradoxical undressing in which a final symptom, or reaction of hypothermia involves the afflicted feeling such a sensation of warmth that he sheds his clothing. To the untrained, or unfamiliar, eye the discarded clothing might suggest a sex-related incident. The lack of clothing on decomposed remains might also imply the death occurred on a hot day or night. In arson scenes the position of the body may appear to be defensive when what is referred to as pugilistic posture is the result of the constriction, but incomplete consumption, of muscles in the presence of extreme heat. Postmortem ambient temperatures are the basis for establishing postmortem interval using insect succession. Citatons in this section may cross-refeence to some under Entomology. Similarly, scene temperatures, over time, influence postmortem characteristics such as lividity and rigor. In that continuum of decomposition temperature is foremost in its rate of advancement. The condition under which a victim’s body might be disposed obviously influences the postmortem context in which it, and associated evidence, is found. In a buried body case of which the compiler is familiar the extremely shallow grave dug by the subject was the result of frozen soils the January night of the murder. Climate, or temperature, impact both taphonomy and geotaphonomy.
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Among all atmospheric hazards, heat is the most deadly. With such recent notable heat events as the Chicago Heat Wave of 1995, much effort has gone into redeveloping both the methods by which it is determined whether a day will be “oppressive,” as well as the mitigation plans that are implemented when an oppressive day is forecast to occur. This article describes the techniques that have been implemented in the development of new synoptic-based heat watch–warning systems. These systems are presently running for over two dozen locations worldwide, including Chicago, Illinois; Toronto, Ontario, Canada; Rome, Italy; and Shanghai, China; with plans for continued expansion. Compared to traditional systems based on arbitrary thresholds of one or two meteorological variables, these new systems account for the local human response by focusing upon the identification of the weather conditions most strongly associated with historical increases in mortality. These systems must be constructed based on the premise that weather conditions associated with increased mortality show considerable variability on a spatial scale. In locales with consistently hot summers, weather/mortality relationships are weaker, and it is only the few hottest days each year that are associated with a response. In more temperate climates, relationships are stronger, and a greater percentage of days can be associated with an increase in mortality. Considering the ease of data transfer via the World-Wide Web, the development of these systems includes Internet file transfers and Web page creation as components. Forecasts of mortality and recommendations to call excessive-heat warnings are available to local meteorological forecasters, local health officials, and other civic authorities, who ultimately determine when warnings are called and when intervention plans are instituted.
From January 1995 through March 2000, temperatures in the passenger compartment of automobiles of different sizes were measured under varying weather conditions (sunshine, cloudy skies, rain) at two locations in eastern Switzerland. During the cold season, the interior temperature rose to 21°C when cars were exposed to sunshine, whereas in summer interior temperature extremes of up to 89°C were recorded. Make, model, and color of the vehicles were of only minor influence.
Summer heat is responsible for a significant number of illnesses and emergency department visits. Although more common in elderly patients, infants, children, and adolescents are also vulnerable. Those involved in the care of pediatric patients need to be aware of the differences in physiology and behavior, as well as predisposing factors that put children at risk. Heat illness constitutes a spectrum of maladies, ranging from the very mild and irritating prickly heat, to severe and potentially life-threatening cases of heatstroke. Milder forms of heat illness respond to removal from the hot environment, rest, and hydration. Heat exhaustion and heatstroke must be recognized early, and rapid cooling and fluid resuscitation must be initiated promptly. Many cases of heat illness can be prevented by paying careful attention to the type of clothing worn, gradual acclimatization to hot and humid conditions, limiting exposure during the hottest part of the day, and drinking fluids both before and during outdoor play or exercise.
An analysis of the important factors for comfort in indoor climate is given. For the thermal complex, the results from calculations of the energy balance model MEMI are used to quantify the effects of the single meteorological parameters on occupants in indoor climate. The quantifications show that besides the air temperature, the mean radiation temperature and the air velocity, especially at very low levels, are also quite decisive for the occupant's mean skin temperature which is used as a measure for comfort. An essential requirement to achieve thermally comfortable conditions in a room is the consideration of the heat transfer resistance of the occupants' clothing and their activity level. A short review of other comfort factors, such as lighting, noise and air quality is given. Finally, three international standards for indoor thermal comfort are discussed.
Thesis--Danmarks Tekniske Høojskole. Summary in Danish. Bibliography: p. 225-240.
Unintentional injuries are the leading cause of morbidity and mortality among children in the United States. This report uses data from the National Vital Statistics System and the National Electronic Injury Surveillance System - All Injury Program to provide an overview of unintentional injuries related to drowning, falls, fires or burns, transportation-related injuries, poisoning, and suffocation, among others during the period 2000 - 2006. Results are presented by age group and sex, as well as the geographic distribution of injury death rates by state.