How to Assess Thermal Comfort at Work

To assess thermal comfort at work, ask who feels uncomfortable, where and when it happens, then examine six factors at the occupied workstation. The four environmental factors are air temperature, radiant heat, air movement and humidity. Clothing and physical workload make up the two personal factors. A thermostat reading covers only part of the first factor and may come from a different part of the room.

Thermal comfort describes how satisfied a person feels with their thermal surroundings. It is possible for a worker by a sunny window to feel too warm while someone in the airflow from a ceiling diffuser feels cold. Begin with the locations and tasks people describe before changing the setting for the whole room.

Start with the complaint at the workstation

Visit during the period when the problem usually occurs. Ask the worker to point out where they feel the heat or draught, what task they are doing and what changes over the shift. A cold draught around the ankles suggests a different investigation from feeling hot across an entire production bay. Include nearby workers whose experience differs. Their answers can help identify the boundary of the problem.

Record the work area, time, occupancy, operating equipment, open doors or blinds, required clothing and any recent change to the building or work pattern. Find out where the thermostat senses temperature and which areas share its controls. Mark an affected workstation and a comparable one where people are comfortable. These give the facilities team somewhere specific to take readings and repeat the check later.

Check the six factors that influence thermal comfort

Use the factors together. A change to one can explain why people report a problem even when the room temperature appears steady. The UK Health and Safety Executive sets them out in its thermal comfort assessment guidance and workplace checklist.

What to check where the person works

Factor	Workstation check
Air temperature	Measure where people sit or stand and when they report the problem. Compare with the building sensor and a nearby unaffected area.
Radiant temperature	Look for direct sun, cold glazing, heated surfaces or nearby process equipment. A surface can warm or cool a person without a large change in surrounding air temperature.
Air movement	Check supply diffusers, doorways, fans and areas of still air. Ask whether the airflow reaches the face, neck or legs and when it starts.
Humidity	Record relative humidity alongside temperature. High humidity makes it harder for sweat to evaporate, particularly during physical work or in clothing that traps moisture.
Clothing	Identify the layers, uniforms and protective equipment the job requires. Record what the worker actually wears and whether they can safely adjust it.
Work rate	Observe the task and its duration. Seated keyboard work, packing at a bench and moving loads generate different amounts of body heat.

Take readings that can explain the pattern

Start with air temperature and relative humidity at the affected and comparison workstations. Note the instrument, location, time, task and building conditions alongside each result. For an air-temperature reading, shield the sensor from direct sun or a nearby hot surface. Record the sun or surface separately because the person may still feel its radiant effect. When complaints recur at intervals, measurements through the relevant part of the shift are more informative than one visit to the thermostat.

A US National Institute for Occupational Safety and Health team used data loggers at nine locations during a commercial office evaluation. Across the locations monitored, temperatures were below the summer comfort guidelines used in that investigation, on the assumptions of seated work and typical summer clothing. Those assumptions are part of what makes the finding interpretable. Apply the same discipline to local readings by recording the work and clothing that went with them. Read the NIOSH office evaluation and its measurement method.

Where readings fail to explain the complaint, ask a competent occupational hygienist or building-services specialist to assess local air speed, radiant conditions or ventilation performance. Persistent disagreement between occupants is itself useful information. The Canadian Centre for Occupational Health and Safety’s office guidance explains how local draughts, windows and individual differences affect comfort.

Match the change to the cause and check the result

Choose a control that addresses the recorded pattern. For afternoon sun at perimeter desks, try shading or moving workstations away from the glazing. For a cold jet from a supply outlet, have facilities review air direction and balance while preserving the ventilation the room needs. For a hot process surface, assess shielding or insulation with the people responsible for the equipment. Set a date to review the change.

Where protective clothing is adding to the heat load, review the task, duration, recovery arrangements and suitable alternatives with the people responsible for worker protection. Required protection must remain effective. A worker who becomes unwell in significant heat or cold needs prompt attention under the site’s emergency arrangements. Heavy work, significant radiant heat or restrictive clothing may call for a separate assessment of workplace heat stress, even when some workers say they feel comfortable. HSE describes when heat requires a separate risk assessment.

Repeat the observations at the same workstations, during comparable tasks and at the time people first identified. Ask both the affected group and their neighbors what changed. Close the issue when the evidence supports the improvement. If redirecting a diffuser helps one desk but moves the draught to the next, the facilities team still has a problem to resolve.

Frequently Asked Questions

The following questions help teams decide what a reading means and when more investigation is warranted.