Controlling thermal comfort

There are a number of ways that you can manage thermal comfort in the workplace:

Administrative controls

Administrative controls include planning and rescheduling work times and practices and rest schedules, for example, scheduling ‘hot’ work for cooler times of day or giving workers flexible hours to help avoid the worst effects of working in high temperatures. Administrative controls are generally of a short term, temporary nature and are also widely recognised as being more expensive and less cost-effective than engineering controls in the long-term.

Engineering controls

These should be the first choice to reduce or eliminate the hazard. Although the initial cost of engineering controls seems high, it has been found that the implementation cost is often offset by the resulting improvements to production and decrease in downtime, with reduced absenteeism and improved motivation.

It is important to stress that any practical solution to controlling thermal comfort is likely to require a combination of different options alongside consultation between employers, employees and their representatives.

Heating

Many types of heating systems are available:

• hot air based heating systems;
• water based central heating systems using radiators;
• combined heat and ventilation systems using air conditioning systems;
• electrical heating systems using electrical heaters;
• under-floor heating systems using either electrical coils or heated fluids;
• overhead heating systems.

Most of these systems are useful. However the beneficial effects may be in some situations restricted to the immediate locality of the heat source.

Air movement

There are many methods for increasing air movement. Small ‘personal’ fans can provide a refreshing movement of air on the face. Larger oscillating fans can provide a swirling air movement, though some people may find this draughty. There may also be noise problems.

Large diameter fans suspended from the ceiling can provide a swirling air movement that is effective over a wide area. Exhaust fans, mounted in the roofs and walls, are useful for removing heated air; however, while improving general air movement, they may have little effect on thermal comfort.

Air conditioning

This can range from small units that lower the air temperature but do not control humidity levels or air movement, to large units that can cope with extreme conditions as well as humidity and air movement.

When air conditioning systems are used, care should be taken to ensure uniform air distribution throughout the workplace, otherwise some workers may complain of feeling cold while others are feeling hot.

Air conditioning units should be operated as per the manufacturers instructions.

Evaporative cooling

Evaporative coolers produce a moderate reduction in air temperature and increase humidity. They operate by passing hot air over water-saturated pads and the water evaporation effect reduces the air temperature.

Thermal insulation

There are many different types of thermal insulation materials, eg loose fills, rock wool and boards. The material acts as a barrier, which slows heat flow in the summer and heat loss in the winter, but it is only effective where there is a temperature difference between the inside and the outside of the building or between two areas inside a building.

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Generic control measures

There are eight main methods of control which you can use:

Control the heat source

• Don't only consider this in relation to air temperature.
• Reduce/increase temperature, humidity, radiant heat load or air movement.
• Insulate the source of heat or cold.

Control the environment

• Replace hot air with cold, or replace cold air with hot, as required.
• Humidify or dehumidify the air as required.
• Increase air movement by ventilation or air conditioning.
• Reduce draught discomfort by directing the ventilation or air movement so that it doesn't blow directly onto the workers.

Separate the source of heat or cold from the worker

• Erect barriers, shield the work area or restrict access.
• Redesign jobs to remove the worker from the area.

Control the task

• Restrict the length of time that workers are exposed to hot or cold conditions.
• Control the amount of work that workers are expected to do.
• Introduce mechanical aids to aid physically demanding jobs in warm and hot environments or when workers are wearing a lot of clothing.

Control the clothing

• If PPE is worn, make sure that workers are not wearing more PPE than is required (ie a higher protection factor than is needed).
• If uniforms are worn, evaluate alternative designs, new materials etc to improve wearability of clothing.
• Evaluate dress code and allow workers to adapt their clothing where possible.
• Multiple layers of clothing enable workers to make reasonable adjustments to their clothing based on their own subjective feelings.

Allow for the worker to make behavioural adaptations

• Where possible, remove all restrictions that may prevent employees from making minor adjustments to their clothing or work rate.
• Provide warm-up or cool-down areas.
• Provide personal heaters or fans.
• Allow workers to adjust thermostats or open windows as appropriate.

Protect the worker

• Provide suitable special clothing and/or equipment (eg desk fans).
• Provide training.

Monitor the worker

• Provide appropriate supervision.
• Obtain medical advice for workers who are pregnant, have an illness or disability, or are on medication.
• As required undertake a specific risk assessment for pregnant workers to identify and manage any risks.

Next: Managers’ guide

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