High Temperatures with Direct Sunlight Exposure


This guideline aims to acquaint business and project owners, and employees with health problems related to working in high temperatures and under direct sunlight. Prevention methods will be provided along with ways to deal with heat related incidents once they occur. In addition, providing recommendations, preventive measure, and raising awareness via a variety of platforms.

In this regard, We must refer to the Ministry of Human Resources and Social Development decision No. 3337 dated 15/7/1435 AH corresponding to 15/05/2014 AD which states, “the worker must not be engaged in open labor under sunlight starting in 2:00 pm till 3:00 pm during the period from the twenty-fifth of June till the fifteenth of September”, and to the great effect such decision has on avoiding many health problems related to working in open locations under direct sunlight and at high temperatures.

The guidelines and directions mentioned herein are merely recommendations (non-binding and not deemed as laws and legislations) issued by the Public Health Authority and based upon adopted international references reviewed by the Authority’s experts. These guidelines and directions target people who work at high temperatures and under direct sunlight and aims to acquaint the workers with the methods of prevention and accommodate with it.

We would like to extend our gratitude and appreciation to Abu Dhabi Department of Health and Abu Dhabi Occupational Safety and Health Center (OSHAD) for issuing the thermal work limit model in geographical areas with high temperatures; including a relevant preventive and standard plans.


Global Warming: The increase in global surface temperature along with an increase in carbon dioxide levels, and an increase in methane gases as a result of the greenhouse gas effect, which contributes to an overall increase in the earth’s atmosphere temperature.

Self-work: It is the work that should allow the workers to adjust their work rate according to environmental conditions.

Non-adaptive Worker: It refers to the non-adaptive worker who is new or those who have been out of work for more than 14 days due to sickness or leave (in a cold climate area).

Light Work: It is working without great effort and is limited to sitting, standing, and moving the arms.

Heavy Labor: It is the work that requires getting up, climbing, lifting, pushing, or use of all body parts to complete the work.

Indoor Workplaces: They refer to indoor workplaces where an appropriate temperature is not less than 20 degrees Celsius maintained at cold places with the availability of cooling equipment in hot places in addition to adequate ventilation for the place.

Outdoor Workplaces (in Open Air): When working in the open air, the weather conditions in this environment can result in dangerous effects to the employee’s safety, and if the risks are not properly considered and managed, this effect might be immediate or might occur on the long run.

Thermal Work Limit Indicator: Thermal working limit is an indicator of thermal stress which gives a measure of the maximum safety rating for working in the important and current environmental conditions (temperature of the dry, wet and radiant thermometer and wind speed), which is designed to encourage workers to drink sufficient amounts of water and stay hydrated, in addition to urging them to organize their work schedule and adapt to the work environment.

Target Group

This guideline targets all those who work in high-temperature environments whether indoor or outdoor. The way of managing the temperature at your workplace depends on whether it is indoors or outdoors and on the normal operating temperature of this environment. You may also need highly specific advice for your workplace for example, concerning thermal stress, drought, heat pressure, and heat strokes that are provided to the government and private institutions, business owners, and workers to help them identify the health problems related to working at high temperatures

Global Warming and its Effect on Workers

The climate expectations indicate an increase in the severity of temperatures and climate emergencies on the global level. Consequently, there might be a loss of jobs and a decrease in the workers’ productivity. The increase in global temperatures due to climate change will make health problems related to high temperatures and direct exposure to sunlight (heat strokes, thermal stress, muscle cramps, skin rash) more common.

The response to the global warming phenomenon must include:

  • An inclusive strategy to mitigate climate change and reduce the extra temperatures
  • Policies and procedures to protect workers in such circumstances
  • Structural reforms to help business owners and workers to take the necessary measures to prepare for climate risks and achieve sustainability and economic growth.

Factors Causing Health Problems for Workers in High Temperatures and Most Vulnerable Group of Workers

The factors causing health problems related to working in high temperatures and under direct sunlight are as follows:

Environmental Factors

  • Global warming and climate change on earth
  • The increase in temperatures and humidity
  • Direct exposure to sunlight or extreme heat
  • Limited air movement (without breeze or wind)


Certain Job-Related Factors

  • High physical exertion
  • Use of heavy and impermeable personal protective clothing and equipment


Workers who are most vulnerable to health problems related to exposure to high temperatures and direct sunlight

  • Those not used to work in high temperatures.
  • Those not used to high physical exertion.
  • Those not used to work outdoors and under direct sunlight.
  • Those suffering from chronic diseases and obesity.
  • Wearing heavy, dark, or tight clothes or using heave personal protective equipment.
  • Those who showed early heat-related symptoms the day before.

Health Problems Related to Working in High Temperatures and Direct Sunlight

Factors of Thermal Stress Affecting the Health

The reason for heat gain in the human body can be a combination of external heat from the environment and internal body heat resulting from metabolic processes. The fast increase in gaining heat due to exposure to more than average heat conditions leads to weakening the body’s ability to organize its temperature and might lead to a range of diseases including heat cramps, thermal stress, heat strokes, and fever.

Death or recovery from heat strokes or diseases resulting from the heat might occur very quickly (in the same day), or may have a delayed effect (after several days) which leads to speeding up death and illness occurrence in people at high risk; especially in the first days of the heat waves. Even the slightest differences from the average seasonal temperatures are associated with increased illnesses and death. Extreme temperatures can worsen chronic conditions such as cardiovascular, respiratory tract and cerebrovascular diseases, and diabetes-related conditions.

Heat also has important non-direct health effects. Heat conditions can change human behavior, contribute to disease transmission, and affect health services provision, air quality, vital social infrastructures such as power, transportation, and water. The magnitude and nature of the heat-health effects depend on the timing, severity, and duration of the temperature, level of adapting to it, and the ability of the local population, infrastructure and institutions to adapt to the prevailing climate. The precise threshold upon which the temperature represents a dangerous situation varies depending on the area and other factors such as humidity, wind, local levels of human adaptation, and preparation for the heat conditions.

Symptoms and Signs of Fever when Working at High Temperatures and Under Direct Sunlight

Headache, dizziness, faintingDebility and generalized weaknessClammy skinIrritability, confusionThirst, nausea, vomiting


Workers’ Health Problems Related to Working at High Temperatures and Under Direct Sunlight:

Heatstroke, thermal stress, muscle cramps, and skin rash.

Symptoms and Signs of Heat Stroke Associated with Working at High Temperatures and Under Sunlight:

ConfusionFaintingHyperhidrosis or red, hot, and dry skinCrampsVery high body temperature (over 40 degrees Celsius)


Symptoms and Signs of Thermal Stress Associated with Working in High Temperatures and Under Sunlight:

Cold and moist skinExcessive sweatingHeadacheNausea or vomitingThe feeling of giddiness and dizziness
Generalized weaknessThirstIrritabilityRapid heart rateHigh body temperature (over 38 degrees Celsius)


Symptoms and Signs of Muscle Cramps Associated with Working at High Temperatures and Under Sunlight:

Muscle spasmPain


Symptoms and Signs of Skin Rash Associated with Working at High Temperatures and Under Sunlight:

Spots of a skin rash accompanied by redness often occur on the neck, upper chest, and skin folds


First Aid to be Followed If a Health Problem Related to Working at Temperatures and Under Direct Sunlight Occurs

Steps to be followed if a worker suffers a heat stroke:

  • Call an ambulance.
  • Place the worker in a shaded and cool area.
  • Remove and loosen the person’s clothes.
  • Help cool and ventilate the person by placing cold compresses and ice packs on the thigh and underarm or soaking the person’s clothes in cold water.
  • Provide fluids (preferably water) as soon as possible.
  • Stay with the person until help arrives.

 Steps to be followed if a worker suffers thermal stress:

  • Call the supervisor at work and ask for medical help.
  • Move the person to a shaded and cooler place to rest with a person staying with it for observing.
  • Give the person cold water as long as it is not unconscious or vomiting.
  • Remove and loosen the person’s clothes.
  • Help cool and ventilate the person by placing cold compresses and ice packs on the thigh and underarm or soaking the person’s clothes in cold water.
  • Take the worker to medical care center or emergency room for medical evaluation or treatment if the signs or symptoms worsen or did not get better.
  • The worker must not return to work on this day even if it gets better.

Steps to be followed if a worker suffers muscle cramps:

  • Make the worker rest in a shaded and cool place.
  • The worker should drink water or other cold drinks.
  • Wait for a few hours before allowing the worker to get back to the hard work.
  • Ask the worker to seek medical care if the cramps do not disappear.

Steps to be followed if a worker suffers a skin rash:

  • Try to work in a cooler and less humid environment whenever possible.
  • Keep the affected area dry.

Preventive Measures for Health Problems Related to Working at High Temperatures and Under Direct Sunlight

Recommendations for Employers

Employers must take the following steps to protect the employees from high temperatures and working under direct sunlight:

  • Set the schedule for performing maintenance and repair works in hot areas at colder times.
  • Set the schedule for performing thermal works at times of the day during which temperatures drop.
  • Enable workers to gradually adapt to the periods of working in hot weather.
  • Reduce the physical demands which the workers have to meet.
  • Hire additional workers or assign tasks that require physical effort to more workers.
  • Provide cold water or fluids for the workers.
  • Avoid drinks containing large amounts of sugar and caffeine.
  • Provide breaks to drink water.
  • Provide cool places to sit during breaks and encourage workers to take separate breaks during working hours in shaded and cold places.
  • Encourage workers to wear sun protection equipment such as head coverings, safety glasses for the eyes, and light-colored clothes.
  • Reduce the physical stress as much as possible by providing the appropriate engineering and electrical tools and equipment (such as electrical lifting equipment).
  • Monitor workers who are prone to thermal stress risk.
  • Appoint an observer for the workers (who is trained in the methods of prevention and dealing with health problems related to high temperatures) while working in a high-temperature environment and under direct sunlight to look for any symptoms or signs of health problems associated with high temperatures.

Providing required training with regards to dealing with health conditions associated with high temperatures in addition to providing information:

  • Risks that threaten workers.
  • Methods of prevention.
  • Monitoring symptoms.
  • The importance of the worker monitoring itself and its coworkers to check symptoms.
  • Personal protective equipment.

Recommendations for Workers’ Supervisors

Workers should avoid exposure to extreme temperatures and exposure to direct sunlight and high humidity whenever possible. If this is not possible, they should take the following preventive steps:

  • Instruct the workers to wear light-colored and loose clothes which allow air permeation such as cotton clothes:
  • Avoid clothes made of synthetic fabrics which prevent air permeation.
  • Progression in performing the works from light to heavy works.
  • Set the schedule for performing the hard work at colder times of the day.
  • Take more breaks at times of extremely high temperatures and humidity.
  • Take breaks in shaded or cool places if possible and provide cold drinking water.
  • Encourage workers to drink water frequently even if they are not feeling thirsty (4 cups per hour).
  • Avoid drinks containing caffeine, alcohol, or large amounts of sugar.
  • Inform workers that protective clothing or personal protective equipment may increase the risk of injury if not used properly.
  • Encourage workers to wear personal cooling tools (such as ice vests and cooling bandanas) and loose and breathable clothing, as long as such items do not pose a danger to safety.
  • Plan for thermal emergencies and train workers for protection against thermal stress and its treatment.
  • Increase the frequency of contacting the workers and encourage them to monitor themselves and others for signs of heat-related diseases.
  • The worker should monitor their physical condition and the physical condition of their coworkers.
  • Ensure the availability of first aid materials on the worksite and the existence of a clear plan to contact medical service providers in case of a medical emergency.
  • Train workers to health problems related to working at high temperatures, methods of their prevention, and how to deal with them if they occur.
  • Prepare a schedule for workers’ rotation so that there are periods for working in an environment with less temperature and away from direct sunlight.
  • Follow the guidelines and times of banning work under sunlight issued by the Ministry of Human Recourses.

Acclimatization and Dealing with New Workers in Hot Areas and the Method of Training them

Acclimatization means the helpful physiological coping which occurs during the recurrent exposure to a hot environment.

This copying includes the following:

Increase the efficiency of sweating:

(Early sweating, increased sweat secretion, reduced salt loss in sweat with recommending not to drink water mixed with salt during work to replace salts)

Circulatory Stability:

Ability to do work with lower core temperature and heart rate increased blood flow to the skin at a certain core temperature.

Acclimatization Schedule:

To acclimatize workers, their exposure time can be gradually increased in hot environmental conditions over the period of 7-14 days. New workers will need more time to adapt than workers who have previously been exposed. As for the new workers, the exposure schedule must not exceed 20% on the first day, and this percentage should be increased by no more than 20% on every additional day.

As for workers who have prior experience in the job, the acclimatization plan should not exceed 50% on the first day, 60% on the second day, 80% on the third day, and 100% on the fourth day.

In addition, the acclimatization level reached by each worker is related to the primary physical fitness of the person and the overall thermal stress suffered by the person.

Preserving acclimatization:

Workers can preserve their adaptation even if they were away from work for a few days, like when going back home to spend the weekend. However, if they were absent for a week or more, there might be a great loss in the helpful adaptations which leads to an increased possibility of developing heat-related diseases and the need to gradually adapt to the hot environment.

Some additional information about preserving acclimatization:

Workers can preserve their adaptation even if they were away from work for a few days, like when going back home to spend the weekend. however, if they were absent for a week or more, there might be a great loss in the helpful adaptations which leads to an increased possibility of developing heat-related diseases and the need to gradually adapt to the hot environment.

  • Acclimatization can often be restored within two to three days upon returning to a job in a high-temperature work environment.
  • People who are in top physical condition certainly preserve better acclimatization.
  • Seasonal changes in temperatures may lead to difficulties in adaptation.

Working in hot and humid environments provides adaptive advantages which also applies to the hot and desert environments and vice versa, which proves that air conditioning has no effect on acclimatization.

Most Dangerous Factors in Increased Temperature and Humidity during Covid-19 Pandemic

During Covid-19 Pandemic, many references recommend that employers encourage workers to wear cloth face masks during work to help reduce the spread of Covid-19; however, workers who wear cloth face masks in a hot and humid environment or during performing hard activities indoors, such as those carried out within bakeries, laundries, electricity utilities, firefighting services, mills, foundries, factories, storage rooms, etc. are likely to suffer some difficulties or discomfort.

Employers should follow the following practices to protect against the spread of Covid-19 and the danger of heat-related diseases:

  • Adapt new and returning workers to the environmental conditions and work while wearing cloth face masks.
  • Give priority to use respirators made of cloth when the workers are in close contact with others (less than one and a half meters), for example during travel, group commuting, or meetings.
  • Evaluate the feasibility of wearing cloth masks for each worker and consider available alternatives (for example, working in places isolated from others or within closed personal offices or using single-use face masks when necessary).
  • Instruct to keep at least (one and half meters) of physical distance in resting areas by way of intermittent breaks, keeping distance between workers, or limiting the number of workers at the break time whenever possible.
  • Follow the air quality criteria in workplaces which include temperature and humidity, as some recent studies indicated the possibility of increased virus spread through dry air.
  • Provide equipped places for rest with moderate temperatures (such as breakrooms or personal vehicles during breaks), which should contain air conditioners or fans while ensuring good ventilation through natural ventilation (such as windows) and exhaust fans, taking into account the physical distancing rules and limiting large number gatherings.
  • In case of use fans for ventilation, avoid directing the fans in a way that pushes the air towards several persons at the same time, as fans may increase the distance from which the respiratory tract droplets can travel.
  • Encourage workers to use cloth face masks made of breathable and moisture-wicking materials to enhance comfort and fitting.
  • Encourage workers to change the cloth face masks when they become wet because wet masks are ineffective and increase breathing difficulty.
  • Provide alternate clean cloth face masks or disposable respirators, as needed, so that workers can change them throughout the work shift. Heat or accumulated moisture can make workers wear and remove the cloth face masks frequently.
  • Ensure the availability of water, soap, and alcohol sanitizer packages at a concentration of (60% to 80%) in toilets, handwashing facilities and urge workers to use them continually, while ensuring good ventilation through natural ventilation (windows) and turning on exhaust fans continuously.
  • Make sure to regularly clean (remove dirt with soap and water) and disinfect (using sodium hypochlorite with a concentration of 1% or alcohol with a concentration of 70%-90%) the high-touch environmental surfaces such as handles, light switches, and faucets.
Note: Face masks made of cloth should not be considered a replacement of engineering and administrative controls, safe work practices, or personal protective equipment especially needed in healthy work zones.


We would like to note that thermal stress is the health condition resulting from the body’s inability to get rid of unhealthy high temperatures when exposed to many internal and external factors.

It may result from a variety of internal or external sources for increased thermal stress, such as:

  • Heat resulting from work processes and machinery (for example, forging).
  • Environmental temperatures, humidity, and lack of air movement (for example, lack of wind or insufficient air circulation).
  • Internal metabolic processes (for example, diseases causing fever).

The heat generated by muscles from physical activity.

Criteria of choosing a temperature indicator and dealing with it

There is more than an indicator to use, and they are as follows:

1 Limit work temperature in work environments

2 Outdoor temperature indicators

The two previous indicators have been chosen based on applying them to work environments similar to the work environment in the Kingdom of Saudi Arabia. The Public Health Authority recommends using the limited work temperature especially in internal and external work environments exposed to different weather conditions such as humidity, wind speed, and high temperatures in dry areas.

1 Limit Work Temperature in Indoor and Outdoor Work Environment

1 When to use the limit work temperature:

  • The limit work temperature is used in indoor and outdoor work environments, during exposure to different weather conditions such as humidity, wind speed, and high temperatures in dry areas.
  • To calculate the limit work temperature, the value of the following measurements should be taken into consideration:
  • Dry thermometer temperature (ambient air temperature) (Celsius)
  • Wet thermometer temperature (humidity/evaporation) (Celsius)
  • Black thermometer temperature (radiant temperature) (Celsius)
  • Wind speed (m/s)

The devices used to take all these measurements and calculate the limit work temperature is internally available. There are also alternate devices that can be used to take the measurements, and then entering these measurements in the electronic calculator to calculate the limited work temperature.

1- Measuring the Limit Work Temperature:

Example of a device


The Public Health Authority recommends the following:

In case of performing heavy works or exposure to thermal stress, the sweating rate increases to 1.2 liters/hour. Consequently, drinking fluids at amounts exceeding this rate is impractical and might lead to intestinal issues and discomfort due to reaching the maximum stomach tolerance to get rid of fluids and excrete them at 1.5 liter/hour rate. Therefore, thermal conditions must be controlled in addition to providing enough water to replace the lost amounts of fluids.


Limit Work Temperature (LWT)- Work Zones

Procedures and Measures- Rest and Work, Schedule of Drinking Water Needs

Work ZonesProceduresSchedule for Needed Amounts of Drinking Water (hours)Schedule for Rest/Work (minutes)

Low risk

Unrestricted zone LWT from 140 to less than 220

There is no danger to the self-work for trained workers who drink large amounts of water

Light work

600 mL/h

This zone is safe for all continuous self-works





Intermediate risk

Warning zone LWT from 115 to less 140




























Caution area refers to the situations where environmental conditions require additional precautionary procedures: practically applying the engineering preventive measures to reduce thermal stress, for example, providing shaded areas and enhancing ventilation. It is not recommended for any person to work alone, nor to hire a nonadaptive person. Make sure to drink enough fluids suitable for the work type.

Light work

1-2.1 L/h

This zone is safe for continuous light self-work

Heavy work

More than 2.1 L/h


Continuous self-work

45 minutes work-

15 minutes rest






High-risk zone

LWT less than 115

Focus on applying the required (work cycle- rest):

It is not recommended for any person to work alone.

It is not recommended to hire a non-adaptive person.

In a high-risk zone, drinking water and identifying the signs of thermal stress should be emphasized. The worker should be equipped with a personal 2 liters water bottle on the site at all times.

All types of work

More than 2.1 L/h

Light work

45 minutes work– 15 minutes rest


Heavy work

20 minutes work- 40 minutes rest

Table No. 1


2 Outdoor Temperature Indicator 

Temperature Measuring Definition:

It means measuring the increase in the ambient temperature of the worker above the limit it cannot endure, which exposes the worker to many risks where death may be the final stage. The source of heat in the work environment may come from natural sources such as sunlight or from industrial sources such as heat resulting from ovens, welding operations, or other work equipment.

Target Group:

All people who work in outdoor work environments with high temperatures according to the table No. 2.

Outdoor Workplaces (in the Open Air)

When working in the open air, the weather effects in this environment can have a very dangerous effect on the employee’s safety, and if the risks are not properly considered and managed, this effect might be immediate or might occur on the long run.

For example, direct exposure to sunlight may cause skin damage including sunburns, blisters, and skin aging and this may lead to an increased risk of developing skin cancer in the long run.

Measuring the Temperature:

The devices used to take these measures are available, some are electronic, and others are mercurial.

Example of a mercurial thermometer.
Example of an electronic thermometer.


When to use a thermometer:

A thermometer can be used to help identify the risks of heat-related diseases for workers in the open air the procedures needed to protect the workers, and when to put such procedures into force. Depending on the value the thermometer indicates, the risks of developing heat-related diseases may range from low to very high to extreme. With the increase of the thermometer indicator value, there is a need for more preventive measures to protect the workers.

The thermometer values are divided into four scopes associated with four risk levels, which help to take the appropriate procedure according to the temperature data. This has been developed for workers to use on worksites according to table No. 2.

Thermometer IndicatorPreventive MeasuresRisk Level
Less than 32.7 degrees CelsiusThermal safety basicsLow (caution)
From 32.7 to 39.4 degrees CelsiusImplement precautions and raise awarenessIntermediate
From 39.4 to 46.1 degrees CelsiusAdditional precautions to protect the workers.High
More than 46.1 degrees CelsiusIssue stricter preventive measuresHigh Risk
Table No. 2


Employers should respond to any high-temperature indicator; such response matches the type of steps to be followed to treat the other risks in the workplace including the following:

  • Train workers on how to identify and prevent heat-related diseases.
  • Monitoring the thermometer on-site daily and notify the workers to take necessary precautions.
  • Implement a preventive plan with constant revision.

Use of protection measures to be taken at each level of risk to notify the workers with the appropriate preventive plan. The plan should address the following:


 Risk Indicator Level
Preventive PlanHigh RiskHighIntermediate



Providing supplies (ensure availability of enough water, provisions for break areas, and other supplies)
Providing canopies, personal protective equipment, fans, steam sprayers, air fresheners, and portable thermometers.)
Emergency planning and response (train supervisors and crews for emergencies)
Workers adaptation (increasing the workloads gradually, allow more frequent breaks so that workers can adapt to temperature)
Modified work schedules (create systems to enable modifications to the work schedule)
Training (train workers to identify diseases related to heat and acquaint them with the relevant preventive measures)
Physiological, visual, and verbal monitoring (using direct observation and monitoring to check for heat-related diseases)


Working on a warmer planet: The impact of heat stress on labour productivity and decent

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Travail par forte chaleur en été: comment agir, INRS, ED, 6371


Public health advice on preventing health effects of heat, World Health Organization 2011





Department of Health – ABU DHABI


HSE executive Indoor / outdoor workplace


WHO heat and health


CDC Workplace Safety and Health