GUIDELINES FOR INDOOR THERMAL COMFORT & VENTILATION
- Introduction
- Hot and Humid Conditions
2.1 Optimal Conditions
2.2 Risks
2.3 Control Measures - Cold Conditions
- References
1. INTRODUCTION
In some indoor workplaces the temperature and air quality may be less than ideal. Some staff and students may experience discomfort as a result. These guidelines provide some information about what can be done locally to improve comfort levels in relatively warm or cool indoor areas whilst acknowledging the environmental and economic impact associated with the increased utilization of mechanical heating, ventilation and air conditioning systems. This information is supplementary to the Air Conditioning Policy published by the Facilities Management Office and relevant projects in the Capital Development Plan to improve indoor thermal comfort and ventilation.
2. HOT AND HUMID CONDITIONS
2.1 Optimal Conditions
Typically staff and student concerns about indoor thermal comfort occur in areas that are poorly ventilated and/or inadequately shaded from sunlight. Individual thermal comfort can also be affected by physical exertion, crowded working areas and some medical conditions. The NSW WorkCover Authority has issued guidelines on indoor thermal comfort which describe optimal conditions for occupational health and safety in an office environment. These are outlined below:
- optimum summer temperature range 21-24 oC
- acceptable summer temperature range 20-26 oC
- optimum humidity range 40-60%
- minimum recommended fresh air rate 10 Litres per second (L/s) per person or 10 L/s per 10 m2 for mechanical ventilation systems
- optimum air movement 0.1-0.5 m/s (naturally ventilated), 0.1-0.2 m/s (air-conditioned).
2.2 Risks
When conditions differ from those listed above, productivity and efficiency are likely to be adversely affected, and in some cases, there may be a risk of dehydration occurring. Lowered concentration due to discomfort can lead to an increased risk of accidents. In addition, some people with existing medical conditions such as heart problems, high or low blood pressure, respiratory conditions and kidney disease may be susceptible to adverse health effects from working in hot and/or humid conditions. Thermal comfort is determined by subjective judgment, and even in optimal conditions some individuals may experience discomfort.
2.3 Control Measures
Local measures that can be taken to alleviate uncomfortably hot and humid conditions and risks of dehydration are:
- use blinds and curtains to minimise sunlight penetration into the workplace
- optimise air movement by using a fan, as air passing over the skin helps to cool the skin
- wear appropriate clothing which enables arms and legs to be uncovered to assist with cooling
- drink plenty of cool water at regular intervals
avoid standing for long periods - negotiate with local management for staff and students to take breaks in cooler and/or less humid areas or transfer some work to cooler and/or less humid areas
- negotiate to alter working hours so that work can be done in the cooler parts of the day such as early morning.
When the temperature in the workplace reaches 30oC the Head of Department should start to consider allowing staff to take rest breaks or even consider suspending work until conditions improve. Factors for the Head of Department to take into account are:
- temperature in the workplace
- humidity level in the workplace, including subjective feelings about this - see below
radiant heat in the workplace - level of physical activity in the tasks being performed by staff - see below
- whether the work performed by staff involves safety-critical tasks such as operating machinery or handling chemicals - see below
- pressure to meet deadlines
- individual conditioning to work in heat and humidity
- specific individual needs such as arising from medical conditions.
Humidity levels cannot be measured readily, but a standard thermometer can be used to give temperature readings. Therefore, recommendations for modifying work activities are based on temperature ranges. When humidity is high, tolerance of high temperatures is reduced, due to the decreased capacity for cooling from evaporation of sweat. Subjective feelings about humidity should be taken into account when considering modifying or suspending work.
Physically demanding work and work that involves safety-critical tasks require careful consideration by the Head of Department in relation to allowing work breaks or suspension of work. For physically demanding work and work that involves safety-critical tasks, the following breaks in work activities are recommended (PSA reference):
30-32 oC: 10 minutes per hour
32-35 oC: 15 minutes per hour
35-36 oC: 30 minutes per hour
37 oC or higher: cease work until conditions improve.
Ideally, breaks should be taken in cool areas. As a minimum, the physically demanding tasks should cease temporarily and staff should rest and consume cool water.
Where the tasks are of a light nature, such as sedentary office work and the temperature in the workplace is 30oC or more for more than two hours, shorter or less frequent rest breaks may be adequate.
In air-conditioned areas, if the air conditioning system is not operating within the acceptable range, report the problem to the Facilities Management Office Service Desk (for Camperdown/Darlington Campus) or local maintenance staff for investigation. If the problem is a complete failure that cannot be repaired promptly and supplementary ventilation cannot be provided (eg windows can't be opened), it may be necessary to leave the area until the system is restored. If the failure relates to temperature control only, and ventilation is still adequate, it may be possible to continue to work in the area by taking local control measures as outlined above.
Note that the use of personal fans or heaters in an air-conditioned area where people are experiencing discomfort may exacerbate the situation. It can actually make the area hotter or colder due to interference with the automatic control system of the air conditioning system. For example, a personal fan may cause a nearby air conditioning thermostat to falsely sense that the room is too cool, consequently increasing the warm air supplied to the room. This exacerbates the already uncomfortably warm environment.
If conditions in non air-conditioned areas are consistently outside the acceptable comfort range, shading, insulation, mechanical ventilation or air conditioning may be warranted. Note that evaporative cooling is not recommended for the Sydney area, but it can be an option in areas where humidity is lower. A risk assessment of the conditions will be required to justify these measures. Refer to the Facilities Management Office Air Conditioning Policy for further details.
In order to improve indoor thermal comfort, concerned staff and students should raise the matter with their supervisor for attention. The Facilities Management Office can provide professional assistance in planning improvements in this area (contact the Service Desk ext. 17838).
3. COLD CONDITIONS
Indoor thermal comfort may also be of concern to staff and students during winter. Reference to WorkCover and Federal Department of Employment and Industrial Relations guidelines gives the following optimum winter conditions:
- optimum winter temperature range 19-22 oC - ie about 1-3 oC lower than summer temperatures
- acceptable winter temperature range 18-24 oC - also lower than in summer
- optimum humidity range 40-60% - the same as for summer
- minimum recommended fresh air rate 10 L/s per person or 10 L/s per 10 m2 for mechanical ventilation systems - identical to summer
- optimum air movement 0.1-0.5 m/s (naturally ventilated), 0.1-0.2 m/s (air-conditioned) - the same as for summer.
When conditions differ from those listed above, productivity and efficiency are likely to be adversely affected. The following short term measures can be taken locally to alleviate discomfort:
- wear appropriate clothing such as wool or other insulating clothing, but ensure it is not too bulky to interfere with work activities
- move around the work area and engage in active tasks as physical activity naturally generates bodily warmth
- use effective room heaters in non air-conditioned areas - see the Risk Management Office Guidelines for Room Heaters. Note that floor model bar radiators are prohibited in the University because of their high risk of starting fires. Note also that overhead radiant heaters are not generally effective and can add to a feeling of discomfort when the head is hot, but the feet remain cold
- in air-conditioned areas, report operational problems to the Facilities Management Office Service Desk (for Camperdown/Darlington Campus) or local maintenance staff for investigation and correction. Note that use of personal fans or heaters in air-conditioned areas where people are experiencing discomfort can exacerbate the problem.
As for hot conditions, staff and students concerned about cold conditions should raise the matter with their supervisor for attention. The Facilities Management Office can provide professional assistance in planning improvements in thermal comfort (contact the Service Desk ext. 17838).
4. REFERENCES
- Department of Employment and Industrial Relations, Working Environment Branch, Office Design at Work - A general guide, AGPS, Canberra, 1983
- Division of Occupational Health/WorkCover Authority of NSW, Heat and Comfort in the Factory and Office, December 1989
- Public Service Association, PSA Heat Policy, November 2000
- University of Sydney Facilities Management Office, Air Conditioning Policy, 1 July 1999
- University of Sydney Risk Management Office, Guidelines for Room Heaters, 1 June 1994
- University of Sydney Risk Management Office, Guidelines for Outdoor Workers Exposed to Ultraviolet Radiation and Seasonal Heat, August 1998
- WorkCover Authority of NSW, Health and Safety in the Office, 1993. (Available on-line at http://www.workcover.nsw.gov.au/ - use the search function and search for "office", then click on the "Health and safety in the office" link. )