Is a workplace safe simply because it is neither too hot nor too cold? Can a temperature that falls within prescribed limits still have a negative impact on employees? And to what extent can inadequate microclimatic conditions affect concentration, work performance and the risk of occupational injuries?
Microclimatic conditions are an important aspect of occupational safety and health, yet their significance is often reduced to whether employees feel comfortable or uncomfortable in the workplace.
In reality, air temperature, relative humidity and air velocity directly affect the body’s thermoregulation, physiological strain, concentration and working capacity.
Inadequate microclimatic conditions can contribute to faster fatigue, reduced attention, an increased number of errors and health complaints. In industrial settings, particularly during physically demanding work, the consequences can be more serious.
Microclimate is therefore not merely a matter of comfort. It is also an employer’s legal responsibility and an important factor in workplace risk management.
What Do We Mean by Workplace Microclimate?
Under the prescribed assessments of the working environment in the Republic of Serbia, three basic parameters are measured:
- Air temperature (°C): affects heat exchange between the human body and its surroundings.
- Relative humidity (%): expresses the actual amount of water vapour in the air relative to the maximum amount possible at a given temperature, and affects the efficiency of sweat evaporation.
- Air velocity (m/s): affects convective heat exchange and the evaporation of moisture from the skin.
However, a comprehensive assessment of thermal comfort and heat stress must also take additional factors into account, particularly the mean radiant temperature of surrounding surfaces, the intensity of physical activity and the thermal insulation provided by clothing.
This means that two workplaces with identical air temperatures may offer very different working conditions.
An employee performing office work at 26°C may experience a completely different physiological response from an employee performing strenuous physical work at the same temperature, particularly when protective clothing is worn.
Temperature: When Do Working Conditions Begin to Threaten Safety?
The human body continuously exchanges heat with its surroundings in an effort to maintain a stable core temperature.
When heat stress increases, the body activates its cooling mechanisms, primarily by increasing blood flow to the skin and producing sweat.
If environmental conditions, physical activity or clothing restrict the body’s ability to dissipate heat, body temperature may rise excessively.
Potential consequences include dehydration, an increased heart rate, fatigue, heat cramps, heat exhaustion and, in the most severe cases, heatstroke.
The risk is not limited to outdoor work. Excessive heat stress can also occur inside industrial facilities, particularly in foundries, bakeries, boiler rooms, production halls and areas with intensive heat sources.
Low temperatures present a different set of risks. Exposure to cold can reduce finger dexterity, cause stiffness, slow motor responses and increase the likelihood of errors when operating equipment.
More severe cold exposure can lead to hypothermia and localised tissue damage.
It is important to understand that the same temperature does not represent the same level of risk for every type of work.
Relative Humidity: Why 26°C Does Not Always Feel Like 26°C
Relative humidity significantly affects how the body experiences thermal conditions.
When relative humidity is high, sweat evaporates less readily from the skin, particularly when the air is close to saturation with water vapour. This limits one of the body’s most important cooling mechanisms.
As a result, working in a warm, humid room can impose a greater heat load than working at the same temperature with lower relative humidity.
Conversely, very dry air can contribute to dry eyes and mucous membranes, particularly during prolonged stays in air-conditioned spaces.
High humidity, combined with cold surfaces and inadequate ventilation, can encourage condensation and mould growth, creating an additional indoor air quality concern.
Relative humidity should therefore never be assessed in isolation from temperature and other workplace conditions.
Airflow: Helpful Cooling or Uncomfortable Draughts?
Air velocity plays a dual role.
In warm conditions, appropriate airflow can help the body release heat and promote sweat evaporation. At lower temperatures, however, or when cold air is directed straight at employees, it can cause local thermal discomfort.
It is particularly important to distinguish ventilation from airflow itself.
Ventilation should provide adequate air exchange and remove airborne contaminants, whereas air velocity describes the local movement of air at the measurement point.
A fan that merely circulates existing air does not necessarily supply enough fresh air or remove hazardous chemicals present in the workplace.
In certain industrial settings, poorly positioned fans can even contribute to the unwanted spread of dust, vapours or other airborne contaminants.
Ventilation and air-conditioning systems must therefore be designed, operated and maintained in accordance with the purpose of the workspace and the characteristics of the technological process.
What Do the Regulations of the Republic of Serbia Require?
Employers’ obligations regarding workplace microclimatic conditions are primarily governed by the Law on Occupational Safety and Health (Official Gazette of the Republic of Serbia, No. 35/2023) and the relevant secondary legislation.
Article 7 of the Law provides, among other things, for preventive measures to ensure that microclimatic conditions comply with the prescribed measures and standards applicable to the relevant industry and workplace.
Article 10 establishes the employer’s obligation to provide appropriate working environment conditions, while Article 15 also covers the engagement of a licensed legal entity to carry out prescribed assessments of workplace environmental conditions.
More detailed requirements are set out in the Rulebook on Preventive Measures for Safe and Healthy Work in the Workplace (Official Gazette of the Republic of Serbia, Nos. 21/2009 and 1/2019).
Under Section 6 of the Schedule of Measures for Safe and Healthy Work in the Workplace, temperatures in work and ancillary rooms must be appropriate to the work methods, activities and physical demands of employees, except where conditions are determined by the technological process.
Section 6.4 refers to Table 1, which specifies air temperature, relative humidity and air velocity values according to the type of work and the outdoor temperature.
What Are the Specific Permissible Values?
For outdoor temperatures of up to +5°C, as well as for the period when outdoor temperatures range from +5°C to +15°C, the Rulebook specifies:
- Light physical work: temperatures between 18°C and 28°C.
- Moderate and heavy physical work: temperatures between 15°C and 28°C.
- Relative humidity: maximum 75%.
When the outdoor temperature exceeds +15°C, the maximum air temperature in the workplace is 28°C, with maximum relative humidity values depending on the air temperature.
For example, Table 1 specifies maximum relative humidity levels of 55% at 28°C, 60% at 26°C and 65% at 24°C.
Air velocity is also subject to limits depending on the category of work:
| Outdoor temperature | Light physical work | Moderate physical work | Heavy physical work |
|---|---|---|---|
| Up to +5°C | 0.3 m/s | 0.5 m/s | 0.5 m/s |
| From +5°C to +15°C | 0.6 m/s | 0.6 m/s | 0.6 m/s |
| Above +15°C | 0.5 m/s | 0.7 m/s | 1.0 m/s |
The values shown are the maximum permissible air velocities specified in Table 1 of the Rulebook.
These values represent regulatory criteria for workplaces covered by the Rulebook. They should not be confused with optimal temperatures or treated as universal thresholds for safe heat exposure.
For example, the fact that 28°C is listed as the maximum permissible temperature does not mean that every work process or level of physical exertion is equally safe at that temperature.
Workplace Microclimate Assessments: When, Where and Who Is Responsible?
The procedure for assessing workplace microclimatic conditions is further regulated by the Rulebook on the Procedure for Inspection and Testing of Work Equipment, Inspection and Testing of Electrical and Lightning Protection Installations, and Testing of Workplace Environmental Conditions (Official Gazette of the Republic of Serbia, Nos. 76/2024, 38/2025, 118/2025 and 57/2026).
Under Article 12, microclimate assessments are carried out at workplaces and in working environments where work is performed, or where employees move around or remain for more than two hours during a work shift.
The prescribed assessments are conducted during both the summer and winter periods. For summer assessments, the outdoor temperature must exceed 25°C; for winter assessments, it must be below 5°C.
The Rulebook requires at least one measurement point in a workplace room of up to 100 m². Larger rooms require a corresponding increase in the number of measurement points. Where the technological process or characteristics of the building require it, the number of measurement points is determined accordingly.
Article 22 requires periodic assessments of workplace environmental conditions to be conducted no later than three years after the previous assessment. Article 21 addresses preventive assessments, including those required after changes that may affect workplace environmental conditions.
For certain working environments with specific technological conditions, such as cold storage facilities, drying rooms and fermentation rooms, Article 12 provides an exemption from this microclimate assessment regime. However, this does not release employers from their obligation to assess and control risks arising from workplace temperature conditions.
Assessments must be carried out by a legal entity holding the appropriate licence, using an accepted methodology, suitable measuring equipment and the relevant regulations and standards.
Why Is Regulatory Compliance Not Always Enough to Assess Actual Heat Stress?
A standard microclimate assessment provides important information about air temperature, relative humidity and air velocity.
However, work involving significant heat stress requires a broader technical assessment.
International practice uses the WBGT (Wet Bulb Globe Temperature) index for preliminary assessment of heat stress by combining relevant thermal measurements.
The standard SRPS EN ISO 7243:2017 governs the use of the WBGT index to assess heat stress.
For the assessment of thermal comfort in moderate thermal environments, SRPS EN ISO 7730:2025 is relevant. It uses the PMV and PPD indices to predict the average thermal sensation and the percentage of people likely to be dissatisfied with the thermal environment.
SRPS EN ISO 7726:2025 is relevant to instrument characteristics and measurement procedures.
These standards provide a more detailed understanding of thermal conditions, but their purpose must be distinguished from mandatory regulatory criteria for workplace microclimate assessments.
In particular, thermal comfort indices should not be used as a substitute for assessing health risks associated with excessive heat stress.
How Much Does Microclimate Affect Productivity?
The impact of inadequate microclimatic conditions extends beyond health complaints.
Heat stress can contribute to fatigue, reduced concentration and a greater likelihood of errors, potentially lowering work performance and increasing the risk of injuries.
In its 2025 technical material on occupational heat stress, the World Health Organization (WHO) reports an estimated 2–3% reduction in productivity for every additional degree Celsius of WBGT above 20°C.
It is important to note that this estimate relates to changes in the WBGT index, not directly to every one-degree increase in ordinary indoor air temperature. Nor is it a universal prediction of productivity loss for every individual workplace.
Nevertheless, it highlights an important business reality: thermal conditions can have a measurable effect on working capacity and efficiency.
In production facilities, this may affect operational quality, work pace, error rates and the need for more frequent breaks.
In office environments, inadequate thermal conditions can contribute to discomfort, increased strain and a reduced perceived ability to concentrate.
Effective microclimate management is therefore both a preventive measure to protect employee health and an investment in the quality of the work process.
What Should Employers Do When Microclimatic Conditions Are Inadequate?
The first step is to establish the actual situation reliably through prescribed assessments and an analysis of the results.
If deviations are identified, their causes should be investigated. These may include inadequate ventilation capacity, process-generated heat, insufficient building insulation, direct solar radiation or an unsuitable layout of workstations.
Preventive measures may include improving ventilation and air-conditioning, insulating heat sources, installing barriers against radiant heat and implementing other technical solutions.
Where technical measures cannot eliminate the heat load entirely, employers should consider work organisation, task scheduling, appropriate rest periods, access to drinking water and procedures for responding to symptoms of heat stress.
Particular attention should be given to employees performing heavy physical work, wearing impermeable protective clothing or working in technological processes involving significant heat stress.
Measures must be defined according to the results of the risk assessment, the characteristics of the work process and employees’ actual exposure.
Conclusion: Microclimate Is a Measurable Safety Factor, Not Just a Subjective Feeling
Microclimatic conditions directly affect employee health, safety and working capacity.
Temperature, relative humidity and air velocity must be assessed together, in the context of the type of work, physical demands and technological process.
The regulations of the Republic of Serbia establish employers’ obligations to provide appropriate working environment conditions, carry out periodic microclimate assessments and implement preventive measures.
However, effective risk management requires more than formal compliance with prescribed values. It requires understanding their impact on employees, recognising specific sources of strain and addressing the causes of inadequate conditions in a timely manner.
A microclimate that meets prescribed values is an important prerequisite for safe work. A microclimate that is also adapted to employees and their work activities provides a foundation for a healthier and more productive working environment.