Industrial heat exposure is not simply a question of whether a workplace feels uncomfortable. In warehouses, workshops and production facilities, excessive heat can become an occupational safety and health risk that requires systematic assessment and appropriate preventive measures.
The challenge is particularly relevant in industrial buildings where high outdoor temperatures combine with solar heat gain, large roof areas, limited air movement and internal heat sources such as ovens, furnaces, dryers, motors, compressors, vehicles and production machinery.
However, air temperature alone does not determine heat stress. Humidity, radiant heat, air velocity, physical workload, clothing, PPE and exposure duration all affect the thermal load experienced by a worker.
This article explains what industrial heat stress is, how it can be assessed, which engineering and organisational controls can be considered, and where industrial ventilation and evaporative air cooling can fit within a wider workplace heat-management strategy.
What is industrial heat stress?
Heat stress describes the overall thermal load imposed on a person by the surrounding environment, the work being performed and the clothing being worn.
It is useful to distinguish between heat stress and heat strain.
Heat stress is the external and internal heat load to which the worker is exposed. Heat strain is the physiological response of the body as it attempts to maintain an appropriate internal temperature.
This distinction matters because two workers exposed to the same measured air temperature may experience very different levels of thermal stress.
For example, a worker performing heavy physical work beside an industrial oven while wearing protective clothing may face a significantly greater thermal load than a worker carrying out light work elsewhere in the same building.
What determines heat stress in a workplace?
A meaningful heat-risk assessment should consider both environmental and work-related parameters.
Air temperature
Air temperature is the most obvious parameter, but it represents only one part of the worker's thermal environment.
Relative humidity
The human body relies heavily on sweat evaporation to dissipate heat. As humidity increases, evaporation becomes more difficult and the body's ability to reject heat can decrease.
Radiant heat
Furnaces, ovens, hot machinery, steam systems and roofs exposed to strong solar radiation can transfer radiant heat directly towards workers.
A normal air-temperature measurement may therefore underestimate the thermal load experienced at a workstation positioned near a strong radiant heat source.
Air movement
Air velocity influences heat exchange between the body and the surrounding environment and can also affect the evaporation of perspiration.
The direction and distribution of airflow are therefore important, particularly when local or zoned cooling is being considered.
Physical workload
The body itself produces heat during physical activity. A worker performing heavy manual work generates considerably more metabolic heat than someone carrying out sedentary or light-duty tasks.
Clothing and personal protective equipment
Protective clothing can limit heat transfer and evaporation from the body. Tasks requiring coveralls, protective suits or other substantial PPE may therefore require additional consideration during heat-risk assessment.
Exposure duration
The duration of exposure matters as well. A short intervention in a hot area is different from a worker spending most of an eight-hour shift at the same hot workstation.
Why a normal thermometer is not enough
A reading of 35°C does not automatically represent the same occupational heat risk in every workplace.
Consider two theoretical environments.
In the first, the air temperature is 35°C but workers perform relatively light work, there is limited radiant heat and substantial air movement.
In the second, the same 35°C air temperature exists next to a furnace, workers perform physically demanding tasks and protective clothing restricts heat loss.
The measured air temperature is identical, but the actual thermal exposure is not.
This is why occupational heat assessment methods consider several parameters together.
WBGT: assessing occupational heat stress
One widely used method for screening occupational heat exposure is the Wet Bulb Globe Temperature, or WBGT.
WBGT is designed to provide a more useful indication of thermal stress than dry-bulb air temperature alone.
Depending on the assessment method and environment, it incorporates measurements that represent factors including:
- air temperature;
- humidity and evaporative conditions;
- radiant heat;
- air movement.
The environmental result is then considered together with factors such as metabolic workload and clothing.
In Spain, the Instituto Nacional de Seguridad y Salud en el Trabajo (INSST) describes the WBGT method in NTP 1189, based on UNE-EN ISO 7243:2017.
Importantly, WBGT should be understood as a screening or first-assessment method, rather than a perfect numerical description of every possible workplace heat situation.
Where the initial assessment indicates significant risk, a more detailed occupational heat assessment may be necessary.
Where does industrial workplace heat come from?
Industrial heat usually results from a combination of external conditions, building characteristics and the production process itself.
External heat
- high summer outdoor temperatures;
- direct solar radiation;
- solar heat gain through roofs and walls;
- warm incoming ventilation air.
Process heat
- industrial ovens;
- furnaces;
- dryers;
- washing and ironing equipment;
- welding processes;
- motors and drives;
- compressors;
- hydraulic equipment;
- vehicles;
- production machinery.
Building characteristics
- large roof areas;
- high ceilings;
- large internal air volumes;
- poorly distributed ventilation;
- limited exhaust paths;
- local areas with stagnant air.
An effective cooling strategy should therefore begin by identifying where the heat originates and where workers are exposed.
Controlling industrial heat: start with the source
Cooling equipment should not automatically be the first or only response to excessive workplace heat.
A technically sound heat-management strategy can combine several forms of control.
1. Reduce heat at source
Where practical, process heat should be prevented from entering the occupied workspace.
Possible measures include:
- insulation of hot equipment and pipework;
- thermal shielding;
- local extraction near heat-generating processes;
- containment of hot process areas;
- reduction of unnecessary heat release.
2. Improve general ventilation
Ventilation can remove accumulated heat and support air exchange through the building.
This may involve natural openings, roof ventilation, extraction systems or mechanically introduced air, depending on the building.
3. Control radiant heat
Where workers are exposed directly to furnaces, ovens or other hot surfaces, barriers, insulation and shielding may be more effective than attempting to reduce the temperature of the complete room.
4. Introduce local or zone cooling
Cooling can be directed towards the actual occupied area rather than the complete building volume.
5. Consider organisational controls
Depending on the risk assessment, appropriate measures may also include changes to work scheduling, recovery periods, task rotation, hydration arrangements, training and monitoring.
Where evaporative air cooling fits
Industrial evaporative cooling is one potential engineering control for workplaces where the environmental and building conditions are suitable.
Rather than using a refrigerant compressor circuit, an evaporative cooler draws warm air through a water-wetted evaporative medium.
As water evaporates, it absorbs heat from the incoming air. A high-volume fan then distributes the resulting cooler airflow into the workspace.
The approach is particularly relevant where large volumes, open doors and continuous air exchange make conventional whole-building air conditioning difficult or unnecessary.
Spot cooling versus whole-building cooling
One of the most important questions in an industrial cooling project is:
Does the complete building need to be cooled?
In many facilities, the answer is no.
Consider a large maintenance hall containing several thousand square metres of floor space and a high roof. Technicians may spend most of their shift working at only a handful of specific positions around vehicles or machinery.
Cooling all of the unused air volume above and around those workstations may provide limited benefit to the people actually exposed to heat.
Spot cooling
One cooler supplies airflow towards an individual workstation or a concentrated heat-exposure area.
Zone cooling
One or more coolers serve a production line, maintenance bay, packing area or another defined part of the building.
Distributed cooling
Several units are positioned around a larger building to create multiple controlled airflow zones.
This approach can be particularly relevant in changing production environments because mobile equipment can be repositioned when workstations or process layouts change.
Humidity and evaporative cooling performance
Relative humidity is a critical engineering parameter when evaluating evaporative cooling.
Dry air has greater capacity to absorb additional water vapour. As a result, hot and relatively dry conditions generally provide greater evaporative cooling potential.
When incoming air is already humid, its capacity to absorb additional moisture is reduced and the achievable supply-air temperature reduction decreases.
Cooler selection should therefore consider temperature and humidity together, not temperature alone.
This is especially relevant across Spain and Portugal, where summer conditions can vary substantially between coastal and inland locations.
Evaporative cooling requires air exchange
Unlike conventional recirculating air conditioning, evaporative cooling normally works with a continuous supply of fresh air.
Because moisture is added during the cooling process, the supplied air needs an appropriate route through and out of the building.
Exhaust paths may include:
- open workshop doors;
- loading bays;
- windows;
- roof vents;
- wall openings;
- mechanical extraction.
A useful way of visualising the process is:
Fresh warm air → evaporative cooler → occupied work zone → air leaves the building
Continuously recirculating the same increasingly humid air will progressively reduce evaporative cooling effectiveness.
When evaporative cooling can be a good fit
Industrial evaporative cooling is particularly relevant where several of the following conditions are present:
- large internal building volume;
- high ceilings;
- regularly open doors or loading bays;
- good possibilities for air exhaust;
- localised operator zones;
- significant summer heat;
- process-generated heat;
- a requirement for high air movement;
- a building that does not require precise temperature control.
When evaporative cooling may be less suitable
No cooling technology is appropriate for every process.
Evaporative cooling requires particular consideration where:
- incoming relative humidity is consistently very high;
- the space must remain tightly closed;
- there is insufficient air exhaust;
- the process requires precise room-temperature control;
- the process requires strict humidity control;
- the principal problem is intense radiant heat that should first be shielded or contained.
Recognising these limitations is an important part of correct system selection.
Workplace heat responsibilities in Spain
Workplace heat management also has an occupational safety dimension.
In Spain, Real Decreto-ley 4/2023, de 11 de mayo amended the workplace requirements established by Real Decreto 486/1997.
The provisions address outdoor work and workplaces which, because of the activity carried out, cannot remain fully enclosed. Preventive measures against adverse meteorological conditions, including extreme temperatures, must be based on the occupational risk assessment and take account of both the work and relevant worker characteristics.
What happens during an orange or red weather warning?
When an orange or red warning for adverse meteorological conditions is issued by AEMET, or where applicable the corresponding autonomous meteorological authority, additional requirements can become relevant.
If the preventive measures already in place do not guarantee adequate protection, adaptation of the working conditions becomes mandatory. The legislation expressly includes the possibility of reducing or modifying the hours of the planned working day.
The framework also provides for certain tasks to be prohibited during periods of adverse meteorological conditions where worker protection cannot otherwise be adequately guaranteed.
This does not mean that installing a cooling system automatically establishes compliance. Cooling, ventilation and airflow management can form part of the technical prevention strategy, but they must be considered within the overall risk assessment.
Workplace heat responsibilities in Portugal
In Portugal, Lei n.º 102/2009, de 10 de setembro establishes the general legal framework for occupational safety and health.
Among other principles, employers are required to ensure safe and healthy working conditions, identify foreseeable risks, evaluate those risks and implement appropriate preventive measures.
The prevention framework gives particular importance to avoiding risks, controlling risks at source and giving priority to collective protection measures where appropriate.
Industrial workplaces and Portaria n.º 53/71
For industrial establishments, the Regulamento Geral de Segurança e Higiene do Trabalho nos Estabelecimentos Industriais, approved by Portaria n.º 53/71 and subsequently amended, is particularly relevant.
Article 24 addresses temperature and humidity and states that workplace conditions should be maintained within suitable limits so that they do not cause harm to workers' health.
Where technological constraints mean that the temperature and humidity conditions cannot reasonably be changed, the regulation identifies possible protective approaches including:
- localised technical measures;
- personal protective measures where appropriate;
- reducing the duration of work periods in the affected location.
This is particularly relevant to industrial heat-management projects because it reinforces the principle that thermal risk can require both engineering controls and organisational measures.
What about Decreto-Lei n.º 243/86?
Decreto-Lei n.º 243/86 contains more specific provisions concerning thermal conditions in commercial, office and service establishments.
Its numerical temperature and humidity references should therefore not be treated as universal industrial limits and automatically applied to every factory or production facility.
For an industrial workplace, the applicable occupational safety framework, industrial workplace requirements, actual process conditions and documented risk assessment should be considered together.
Cooling equipment does not replace a heat-risk assessment
This point is important both technically and legally:
Installing an industrial air cooler does not by itself demonstrate that workplace heat risk has been adequately controlled.
Depending on the process, a complete prevention strategy might combine:
- heat-source insulation;
- radiant-heat barriers;
- process extraction;
- general ventilation;
- local or zoned cooling;
- work scheduling;
- work and recovery periods;
- hydration arrangements;
- employee training;
- environmental monitoring;
- periodic review of the risk assessment.
Evaporative cooling can therefore be considered as one engineering measure within a wider occupational heat-control strategy.
Typical industrial applications
Heat-management requirements vary significantly by industry. Common applications for targeted industrial cooling include:
Industrial laundries
Washers, dryers, finishing systems and ironing lines continuously introduce heat into occupied working areas. In demanding laundry applications, production areas can reach approximately 40–45°C.
Metalworking and heavy industry
Furnaces, extrusion lines, welding, machining and other hot processes can combine elevated air temperature with significant radiant heat.
Food production and bakeries
Ovens, baking tunnels, dryers and hot process equipment can create concentrated thermal loads around operators and production lines.
Automotive workshops
Garages and maintenance workshops commonly have open doors, large volumes and technicians positioned around vehicles, making local cooling a practical strategy.
Rail and bus maintenance
High-bay depots can contain extremely large air volumes while technicians work within much smaller zones around trains and buses.
Paper, cardboard and printing
Paper machines, corrugators and high-speed printing equipment can generate heat continuously along extended production lines.
Information required to assess an industrial cooling application
An initial industrial cooling assessment should consider:
- workspace floor area;
- ceiling height;
- total building volume;
- typical summer temperature;
- relative humidity;
- location and type of internal heat sources;
- existing ventilation and extraction;
- open doors and loading bays;
- number and location of workers;
- physical workload;
- airborne dust and contamination;
- operating hours and seasonal requirements.
This information helps determine whether spot cooling, zone cooling or distributed cooling is likely to provide the most appropriate approach.
Industrial evaporative cooling capacity
Mobile evaporative air coolers are available for working areas ranging from relatively small local zones through to much larger industrial spaces.
The current Filtra International range covers airflow capacities from approximately 5,000 to 48,000 m³/h, with nominal model recommendations extending from approximately 60 to 600 m².
These area values are useful as initial selection guidelines, but they should not replace consideration of building height, heat load, ventilation, temperature, humidity and workstation position.
Professional configurations are available for relatively clean environments, while industrial configurations add G4 incoming-air pre-filtration for demanding workshops, production facilities and warehouses.
Purchase or rental?
Industrial heat is frequently seasonal, which means permanent equipment ownership is not always the only suitable option.
Filtra International supplies industrial evaporative air coolers for both purchase and rental, subject to equipment availability.
Rental can be useful for temporary production requirements, seasonal heat, short-term projects or facilities that only require additional cooling during the warmest months.
Related technical resources
For a detailed explanation of the cooling technology, model selection, ventilation requirements and available configurations, see our Industrial Evaporative Air Cooling technical guide .
Available equipment can be found in our Industrial Evaporative Air Cooler collection .
Frequently asked questions
What is industrial heat stress?
Industrial heat stress is the thermal load placed on a worker by environmental conditions, physical workload and clothing. Air temperature is only one factor; humidity, radiant heat, air velocity and metabolic workload are also important.
Is air temperature enough to assess workplace heat?
No. Two workplaces with the same air temperature can create very different levels of thermal stress depending on humidity, radiant heat, air movement, workload and protective clothing.
What is WBGT?
WBGT stands for Wet Bulb Globe Temperature. It is a commonly used screening index for occupational heat stress that incorporates environmental thermal factors and is evaluated together with workload and clothing.
Can evaporative cooling reduce workplace heat stress?
Evaporative cooling can form part of an engineering heat-control strategy by reducing incoming air temperature and supplying controlled high-volume airflow to occupied zones. Its effectiveness depends on factors including temperature, relative humidity and ventilation.
Does evaporative cooling work in humid conditions?
Cooling potential decreases as incoming air humidity increases because the air has less capacity to absorb additional water vapour. Temperature and relative humidity should therefore always be considered together.
Does Spanish law address extreme heat at work?
Yes. Spanish occupational safety requirements include measures for adverse meteorological conditions in outdoor work and workplaces that cannot remain fully enclosed because of their activity. During relevant orange or red meteorological warnings, working conditions may have to be adapted where existing preventive measures do not provide adequate protection.
Does Portuguese legislation address heat in industrial workplaces?
Yes. Portugal's general occupational safety framework requires employers to assess foreseeable risks and implement prevention measures. Industrial workplace regulations also address temperature and humidity and provide for localised technical protection or reduced exposure time where thermal conditions cannot reasonably be changed.
Does installing an air cooler automatically make a workplace compliant?
No. Cooling equipment is one possible engineering control. Compliance and worker protection depend on the complete risk assessment and the combination of technical, organisational and other preventive measures appropriate to the workplace.
References and further reading
- Instituto Nacional de Seguridad y Salud en el Trabajo (INSST) — NTP 1189: Evaluación del riesgo de estrés térmico: Índice WBGT.
- Spain — Real Decreto 486/1997, de 14 de abril, on minimum safety and health requirements in workplaces.
- Spain — Real Decreto-ley 4/2023, de 11 de mayo.
- Portugal — Lei n.º 102/2009, de 10 de setembro, Regime jurídico da promoção da segurança e saúde no trabalho.
- Portugal — Regulamento Geral de Segurança e Higiene do Trabalho nos Estabelecimentos Industriais, approved by Portaria n.º 53/71 and amended by Portaria n.º 702/80.
This article provides general technical information about workplace heat management and should not be considered legal or occupational-health advice. Employers should assess the requirements applicable to their specific workplace, activities and workforce.