In Brief

Cooling controls should reduce environmental or metabolic heat load; a sensation of coolness does not prove risk is controlled.
Elimination, insulation, enclosure, ventilation and mechanisation take priority over personal cooling products.
Fans may be ineffective or counterproductive where air is hotter than skin, contaminated or very humid.
Cooling garments require assessment of duration, weight, compatibility, hygiene and recharge arrangements.
Control performance should be verified through representative monitoring, observation and worker feedback.

Start With the Heat Balance

The body gains heat from physical work and the surrounding environment. It loses heat through radiation, convection and evaporation of sweat. A useful control changes one or more of those pathways: it reduces metabolic effort, blocks radiant heat, lowers air temperature, increases beneficial evaporation or creates genuine recovery.

This distinction prevents an employer buying a product simply because it feels cold at first. A towel may provide temporary comfort yet warm rapidly. A fan may improve evaporation in dry moderate air but move hot air or contaminants towards a worker. An ice vest may remove heat while adding weight and restricting movement.

HSE advises considering air and radiant temperature, air movement, humidity, clothing and work rate. Duration and recovery also matter. Select controls only after assessing that combined thermal load and the other hazards present.

Meet UK Duties Through Risk Control

Great Britain has no universal maximum workplace temperature. Employers nevertheless have duties under the Health and Safety at Work etc. Act 1974 and Management Regulations to assess and control foreseeable risk. Indoor workplaces must have a reasonable temperature under the Workplace Regulations.

HSE’s heat-stress guidance describes assessment and control but does not turn every example into a fixed legal prescription. Employers should document why a cooling method suits the task and how it contributes to a wider safe system.

Required personal protective equipment remains governed by the PPE at Work Regulations. Cooling equipment worn on the body must not compromise chemical, flame, electrical, respiratory or fall protection. Compatibility should be confirmed through competent assessment and supplier information.

Remove or Reduce the Heat Source First

Eliminate unnecessary presence in the hot area through remote inspection, automation or relocating controls. Reduce process temperature where possible and schedule shutdown work after adequate cooling. Replace manual handling with mechanical aids to lower metabolic heat.

Insulate hot pipes, vessels and surfaces. Install radiant shields between the source and worker, ensuring they do not obstruct access, ventilation or emergency escape. Enclose a hot process and extract heat at source rather than cooling an entire building inefficiently.

Separate occupied workstations from heat-generating plant and provide cooled cabins or control rooms. Doors and windows must support the design; a cooled refuge with frequently opened doors may not perform as intended. Maintain seals, insulation and cooling equipment.

Source control usually protects more people and operates continuously. Personal cooling remains useful where engineering controls cannot fully manage residual or temporary exposure.

Use Ventilation and Fans With Care

Ventilation can remove hot air and introduce cooler replacement air. Local extraction may capture steam or hot process emissions, while general ventilation dilutes accumulated heat. Design must consider airflow paths, make-up air and interaction with contaminant controls.

Fans increase air movement and can improve sweat evaporation when conditions allow. High humidity limits evaporation. Where air temperature is very high, increasing convection may add heat rather than remove it. HSE also warns that air movement should not expose workers to another risk.

Do not place comfort fans where they disrupt local exhaust ventilation or spread dust, vapour, biological contamination or hot exhaust. Assess people downstream. In hazardous areas, electrical equipment must be suitable for fire and explosion risk.

Air conditioning can cool enclosed rooms effectively, but capacity must reflect occupancy, process heat and door opening. Maintain filters, condensate and refrigerant systems. A portable unit that exhausts heat into the same room may provide little net benefit.

Control Radiant and Solar Heat

Radiant heat travels directly from hot surfaces or the sun and can be significant even where air temperature is lower. Reflective or insulated barriers can reduce the worker’s view of the source. Position them close enough to interrupt radiation without creating contact burns or trapping heat around equipment.

Outdoor shade should cover the task where practicable as well as the rest area. Consider sun movement, reflective roofs and hardstanding, wind loading and stability. Shade structures must not introduce work-at-height, lifting or vehicle hazards.

Move outdoor work to cooler periods and provide mechanical aids. UV exposure is related but distinct: shade, suitable clothing and skin protection should address solar radiation without adding excessive thermal insulation.

Design Real Recovery

Recovery works when the worker reaches a cooler environment, reduces activity and can remove unnecessary PPE safely. Count travel, decontamination and doffing time. A break beside the same furnace or in a hot vehicle is not thermal recovery.

Locate cooled or shaded areas close to the work and provide seating, clean drinking water and enough capacity for the team. Determine work–recovery cycles from competent assessment of conditions, workload and clothing. Fixed schedules copied from another workplace may be unsuitable.

Review recovery as conditions change. A morning pattern may fail during an afternoon peak or ventilation fault. Give supervisors authority to extend recovery or suspend work.

Evaluate Cooling Garments

Cooling vests use phase-change materials, ice, circulating liquid, compressed air or evaporation. Each has limitations. Ice products can be very cold initially, then lose effect; phase-change packs offer a more controlled temperature but require recharge; air or liquid systems may tether movement; evaporative products perform poorly at high humidity or beneath impermeable clothing.

Assess the complete system:

cooling capacity and effective duration;
added mass and metabolic effort;
fit, mobility and posture;
compatibility with PPE and harnesses;
recharge or replacement logistics;
cleaning, contamination and infection control;
failure recognition and disposal;
suitability for electrical or explosive atmospheres.

Trial equipment with representative workers and tasks. Do not rely solely on manufacturer claims. A product that works in a laboratory may perform differently beneath encapsulating PPE or during climbing.

Cooling should not mask symptoms and encourage longer exposure beyond assessed limits. Establish a conservative replacement point and provide enough units for the planned work and delays.

Clothing, PPE and Evaporation

Ordinary work clothing influences heat exchange. Loose, breathable clothing may support evaporation where the task permits, but exposed skin can increase risks from chemicals, abrasion, flame or ultraviolet radiation. Select clothing through the full risk assessment.

Impermeable protective suits restrict evaporation. Reduce exposure duration, workload and retained heat through engineering and organisational measures. Remove PPE promptly once it is no longer required, following contamination-control procedures. Provide drying and replacement arrangements.

Never instruct workers to loosen fasteners or remove required PPE in the hazardous area. If workers repeatedly do so, treat that behaviour as evidence that the system is not tolerable and redesign the work.

Hydration Supports but Does Not Cool the Process

Provide accessible cool drinking water and regular opportunities to drink. Hydration supports sweating and circulation but does not reduce radiant heat, workload or clothing insulation. A hydration campaign should never justify continuing an excessive exposure.

Avoid rigid universal intake targets. Needs vary, and excessive water consumption can be harmful. Workers with medical fluid restrictions need confidential occupational-health advice. Maintain hygienic containers, convenient toilets and welfare that encourages appropriate drinking.

Acclimatisation and Work Design

Gradual repeated exposure helps the body adapt. New starters and people returning after absence need progressively increased heat work over several days. Adaptation depends on environment, workload, clothing and individual response and can be lost.

Acclimatisation is not a cooling technology and does not permit avoidable high exposure. Combine it with reduced pace, cooler scheduling, mechanical assistance, adequate staffing and close supervision. Rotation is beneficial only when the alternative task reduces total heat load.

Verify That Controls Work

Define the expected outcome before a trial: lower radiant exposure, reduced WBGT, longer stable operation without symptoms, or improved recovery. Select measurements and observations that answer that question. Air temperature alone may miss the change.

Record operating conditions before and after installation. Check ventilation flow, shield position, cooling duration, recovery temperature and worker response. Consider uncertainty and repeat under representative peak conditions. Investigate symptoms regardless of readings.

Inspect and maintain controls. Dirty coils, failed fans, missing insulation and unrecharged packs can silently reduce performance. Provide simple pre-use checks and a defect-reporting route. Review after process, building, clothing or staffing changes.

Sysco Environmental can support task-based heat assessment and verification of cooling controls. Our approach is to determine which heat pathway dominates and test whether the selected measure changes exposure in practice.

Effective cooling is a system, not a product list. Reduce heat at source, lower physical effort, provide genuine recovery and use personal cooling for defined residual risk. Evidence should show that the control protects people throughout the task, not merely that it feels cooler at the start.

Cooling Workers or Masking Risk? Choose Controls That Work