Heat stress in Night Clubs
HEAT STRESS IN NIGHT-CLUBS
by Marc McNeill and Ken Parsons, Department of Human Sciences, Loughborough
University of Technology, UK
An Internet survey of behaviour, attitudes and opinions of regular club-goers
found that night-clubs were considered to be hot or very hot places where
many respondents experienced heat related illnesses. The thermal conditions
of a night-club were measured (maximum 29°C air temperature, 90% relative
humidity) and simulated in a thermal chamber. Four male and four female
subjects danced for one hour. The results showed a rise in core temperature
(mean=1.8°C, sd=0.26) and skin temperature (mean=1.34°C, sd=0.48)
and a sweat rate of almost ll/h. Subjects generally felt hot and sticky,
preferring to be cooler. The physiological responses compared well with
predictions from ISO 7933 and the 2-node model of human thermoregulation
(Nishi & Gagge, 1977). The predicted effects of continuous dancing for
four hours gave a core body temperature increase to 39.1°C, well above
the WHO limit of 38°C in occupational settings. Using ISO 7933 appropriate
work-rest schedules for dancing and water requirements were suggested.
Every weekend an estimated half a million people in the UK go to raves (all
night dance parties) and night-clubs (Jones, 1994). They go to dance, often
for long periods of time. The ambient thermal conditions of the night-clubs
they dance in are o~en hot and humid. This can put considerable heat stress
on those dancing.Since 1988 there have been approximately 16 fatalities
in UK night-clubs (Henry, 1992; Arlidge 1995). Whilst drugs were often implicated,
in most instances heat-stoke was the actual cause of death. It is likely
that there are also many less serious heat related problems.
The principle aims of this investigation were to assess the thermal conditions
in night-clubs and to quantify the behavioural, physiological and subjective
responses of people dancing in them. The study comprised of 4 parts, a survey
of behaviour in, and opinions on the thermal conditions in night-clubs;
an assessment of the thermal conditions of a night-club, measurement of
subjective and physiological responses of dancers in simulated night-club
thermal conditions and an evaluation of the accuracy of predictive thermal
models in order predict the physiological responses to night-club thermal
conditions over a period of time.
Survey of behaviour, attitudes and subjective responses to thermal conditions
The population was identified to be predominantly young people (Jones 1994),
covering a geographically scattered area. A questionnaire was distributed
to subscribers on the UK-Dance discussion group on the Internet and to people
outside night-clubs. In total 54 subjects responded to the survey, 65% male,
Night-clubs were considered to be hot or very hot places where 61% of people
would prefer to be cooler. Respondents generally preferred to drink soft
drinks rather than alcohol, many (76%) used drugs such as 3,4-methylenedioxymethamphetamine
(ecstasy) for their stimulation. High priced bottled water and disconnected
water supplies were given as reasons for low consumption of liquids. In
such environments with increased metabolic activity from dancing dehydration
was likely, indeed 88% of respondents had experienced heat related illnesses.
Thermal Audit in a Night Club
Night clubs vary in architecture and interior design and each is unique.
The auditorium investigated represented a large, high ceiling type, typical
of many institutionalised auditoria. Using a Grant Squirrel data logger
fixed in the lighting rig, air temperature, radiant temperature and relative
humidity were recorded every five minutes over a period of three nights.
A maximum air temperature of 27°C and 82% relative humidity were recorded
in the auditorium during each night. These measurements were made at approximately
2m above head height. Using a hand held Solex humidity/temperature meter
the maximum air temperature and relative humidity amongst those dancing
were 29°C and 90% respectively. Air velocity in the empty auditorium
was 0.175m/s. With a total of 180 lamps rated between 150-750 watts a significant
radiant heat load was expected, however the positioning of the Squirrel
data logger prevented the black globe being placed under any direct radiant
load, hence the true extent of this thermal load was not seen in the results.
Investigation into the Physiological Responses in a Night-Club
The thermal conditions of the auditorium were simulated in the thermal chamber.
A pilot study was conducted to evaluate and improve the experimental methods.
Aural, oral and Ramanathan's four point mean skin temperature (Parsons 1993),
metabolic rate, heart rate and amount of sweat loss were all measured. Eight
subjects were exposed to the
experimental conditions over two sessions. In each session there were four
subjects, two males and two females with a mean age of 21.75 years and wearing
clothing of an estimated value of 0.7 clo. They were weighed semi-nude then
thermistors were securely attached. Subjects danced for 30 minutes with
their metabolic rates being taken using the Douglas bag method for 2 minutes
after 25 minutes. A five minute break allowed them to rest whilst the music
was changed. They then continued to dance for the remaining time, their
metabolic rates again being taken after 55 minutes.
Finally they were weighed semi-nude with their clothes being weighed separately
in a plastic box. All measurements were repeated to ensure accuracy. After
weighing they were given soft drinks, offered a shower and discussed the
The mean aural temperature rose gradually for 15 minutes before flattening.
The inadequacies of the measuring techniques for this application were identified.
The ear thermistors for three subjects lost contact and were therefore unreliable.
When these results were removed, the mean rose to a maximum of 38.2°C,
sd=0.25 (Fig 1). The mean 4 point mean skin temperature rose at a similar
rate from 36.9°C-38.2°C sd=0.5. The five minute break was sufficient
to elicit a decrease in skin temperature of 0.56°C.
The anticipated difference in metabolic rate between the two different styles
of music was not found. The discrepancy between the actual and expected
results may have been due to more athletic dancing in response to preferred
music being heard.
Heart rate was sustained at a mean of 140 bpm. The heart rates of the females
(who were considered to be fitter) were lower than those of the males. The
heart rate was correlated with the measured metabolic rates in order to
estimate the mean metabolic rate for dancing to be 238 W/m2.
The results suggested that night-clubs present stressful conditions to those
dancing. It was not possible to assess the effects of a prolonged exposure
in the simulated conditions. The 2-node model of human thermoregulation
(Nishi & Gagge, 1977) and ISO 7933 were therefore used to predict how
the human thermoregulatory system responds to night club conditions over
an extended period of time. The thermal conditions found in the night-club
were used in the models, air and radiant temperature being 29°C, air
velocity 0.175m/s and relative humidity being either 70% or 90%, the later
being the maximum humidity recorded. A metabolic rate of 238W/m2 was used.
The models were run on PC's, the predictions generated being compared with
the results from the laboratory investigation to evaluate their accuracy.
The 2-node model over estimated the 4 point skin temperature. It was more
accurate with core temperature, (Fig. 1). The predicted core temperature
did not account for the five minute rest that was observed in the actual
core temperature. Towards the end of the experiment the actual temperature
exceeded the predicted temperature. This may have been due to the increase
in activity by subjects towards the end of the investigation. ISO 7933 also
accurately predicted trends in the rise of core body temperature. The effects
of a four hour exposure were then predicted, this being the mean time that
in the survey danced for. The 2-node model predicted a core body temperature
increase to 39.07°C (table 1). This is well above the WHO limit of 38°C
in occupational settings. Using ISO 7933 appropriate work-rest for dancing
and water requirements were suggested. This can be seen in table 2.
Conclusions and Recommendations
1. Night-clubs operate at stressful temperatures and humidity. This can
dancing in them to heat strain. Suitable measures such as increased air
be taken to reduce the thermal stress.
2. "Chillout" rooms at lower temperatures to the main dance floor
should be provided for
rest and cooling of body temperature.
3. Frequent rests should be taken between periods of dancing; after 40 minutes
dancing, a 20 minute rest should be taken in a "chillout" room.
4. Adequate amounts of water should be consumed by those in night-clubs
dehydration. It is suggested that this should be 1 litre/hour for active
dancing, however over consumption of fluids should also be avoided and advice
should be provided.
5. Provision of free, cool, drinking water should be made compulsory.
6. The 2-Node predictive model for human response to thermal enviromnents
proved to be
a fairly good representation of the actual environment observed. With care
this can be
used to make further predictions.
7. ISO 7933 accurately predicted the times of exposure before alarm limits
and over-estimated times before danger limits were reached.
8. Club goers should be educated as to the risks of heat strain illustrated
in this report.
This could be made possible with a simple wet bulb globe thermometer (WGBT),
displaying the thermal conditions in clubs and the likely effects of dancing