Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

September 1, 2021

Deputy Assistant Secretary
KIMBERLY STILLE, Acting Director
Directorate of Enforcement Programs
Inspection Guidance for Heat-Related Hazards

This memorandum establishes an enforcement initiative to prevent and protect employees from serious heat-related illnesses and deaths while working in hazardous hot indoor or outdoor environments.  It expands on the agency’s ongoing heat-related illness prevention campaign by setting forth the enforcement component and reiterating its compliance assistance and outreach efforts.  The initiative prioritizes heat-related interventions and inspections of work activities on days when the heat index exceeds 80℉.  Employers will be encouraged to implement proactive interventions, such as water, rest, and shade, and other important prevention measures such as acclimatization of new or returning workers.

Background:  The U.S. Department of Labor’s Bureau of Labor Statistics (BLS) reports that from 2011 to 2019, environmental heat cases resulted in an average of 38 fatalities per year and an average of 2,700 cases with days away from work.  Heat-related illnesses range from heat cramps to heat stroke, which can lead to death.  Between 2015 and 2020, Federal OSHA has conducted approximately 200 heat-related inspections each year, with about 15 heat-related fatality inspections annually.  Many of these inspections resulted in OSHA citations under the general duty clause, Section 5(a)(1) of the OSH Act, for exposing workers to heat-related hazards.  However, the total number of heat-related fatalities may be underreported.  The cause of death is often listed as a heart attack, when the actual cause was exposure to a heat-related hazard. 

Serious heat-related illnesses occur when the body temperature exceeds 100.4 degrees Fahrenheit (100.4°F).  Fatal heat-related cases are usually the result of exertional heat stroke, where physical activity in hot environments causes the body temperature to reach 104°F or higher (normal body temperature is around 98.6°F).  Attachment 1 of this memorandum provides a list of serious heat-related illnesses, along with common signs and symptoms.[1] 

Heat-related illnesses generally occur when body heat generated by physical work is performed in conditions of high ambient heat, especially when combined with humidity and inadequate cooling.  Combinations of heat and humidity are used to determine the commonly used “feels like” (i.e., or heat index, or HI) temperature.  The National Weather Service  (NWS) uses heat index to classify environmental heat into four categories: Caution (80°F - 90°F HI ), Extreme Caution (91°F - 103°F HI), Danger (103°F - 124°F HI), and Extreme Danger (126°F or higher HI). 

The National Institute for Occupational Safety and Health (NIOSH) has published recommended occupational exposure limits and controls for heat stress.  A NIOSH publication, Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments, outlines recommended environmental limits for physical work at which point engineering controls, preventative work, hygienic practices, and administrative or other control procedures should be implemented in order to reduce the risk of heat-related illnesses.  NIOSH has a Recommended Alert Limit (RAL) and Recommended Exposure Limit (REL) based on the Wet-Bulb-Globe Temperature (WBGT).[2]  

Heat-related illnesses can happen at almost any ambient temperature, especially in cases where workers perform moderate or higher physical activity, wear heavy or bulky clothing, or equipment.  Area Offices should become familiar with the various types of warnings, alerts, and advisories, issued by the U.S. National Oceanographic Atmospheric Administration (NOAA) National Weather Service (NWS).  Among them are the following:

  • Heat Advisory—A Heat Advisory is issued within 12 hours of the onset of extremely dangerous heat conditions.  The general rule of thumb for this Advisory is that the maximum heat index temperature is expected to be 100°F or higher for at least 2 days, and night time air temperatures will not drop below 75°F. 
  • Heat Wave— A heat wave is forecast by NWS or a local news station.  A heat wave is when the daily maximum temperature exceeds 95°F or when the daily maximum temperature exceeds 90°F and is 9°F or more above the maximum reached on the preceding days.
  • Excessive Heat Warning—An Excessive Heat Warning is issued within 12 hours of the onset of extremely dangerous heat conditions.  The general rule of thumb for this Warning is that the maximum heat index temperature is expected to be 105°F or higher for at least 2 days and night time air temperatures will not drop below 75°F.
  • Excessive Heat Watches—Heat watches are issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours.  A Watch is used when the risk of a heat wave has increased but its occurrence and timing is still uncertain; and
  • Excessive Heat Outlooks— Outlooks are issued when the potential exists for an excessive heat event in the next 3-7 days.  An Outlook provides information to those who need considerable lead-time to prepare for the event.

While all of these alerts and advisories can serve to signify ‘heat priority days’ (i.e., days in which a maximum heat temperature can result in increased risks of heat-related illnesses), these criteria vary across the country.  Particularly in areas of the United States that are not usually subject to elevated dangerous heat conditions, unacclimatized workers may suffer serious heat-related illnesses even when the heat index is not high enough to trigger NWS heat advisories or warnings. 

When the heat index exceeds 80°F, serious occupational heat-related illnesses become more frequent, especially when unacclimatized workers are performing heavy strenuous work (e.g., intense arm and back/lifting work, carrying, shoveling, manual sawing, pushing and pulling heavy loads and walking at a fast pace), without easy access to water or shade, or working in direct sunlight.  Heat-related fatalities have occurred with a heat index below 80°F, particularly when these aggravating factors are present.  This initiative identifies heat priority days as those days with a heat index that exceeds 80°F.[3]  A heat index at this level indicates a need to increase enforcement efforts to identify potential heat-related hazards present in working conditions before the occurrence of an illness or death.  

Employers have a duty to prevent heat-related illnesses and deaths in both indoor and outdoor workplaces.  Record hot temperatures create excessive heat working conditions that are especially dangerous to workers who have not been acclimitized.  Acclimitization is a process by which a person gradually increases their exposure time in hot environmental conditions, causing beneficial physiological changes to prevent heat-related illnesses by properly regulating body temperature.  It is essential for employers of new or returning workers to gradually increase their workloads and ensure more frequent breaks as they acclimatize to ambient conditions.  However, the most successful efforts to prevent heat-related illnesses and deaths include more than just worker acclimitization programs.  A resource for best practices on worker acclimatization is the American Conference of Governmental Industrial Hygienists (ACGIH®) Action Limit (AL) for unacclimatized workers and a Threshold Limit Value (TLV®) for acclimatized workers, see Heat Stress and Strain: TLV® Physical Agents 2021 Edition,  Employers should use a combination of intervention methods, including encouraging or mandating that employees regularly take breaks for rest, shade, and supplying water.  Employers should train employees on heat-related illnesses, how to spot common symptoms, and what to do when a worker suspects a heat-related illness is occuring.  Employers should also take periodic measurements to determine employees’ heat exposure and provide protection to employees from heat as necessary.

Scope:  This initiative applies to indoor and outdoor worksites where potential heat-related hazards exist.  Working conditions that have resulted in serious heat-related illnesses occur in all major industry sectors of employers, including general industry, construction, agriculture, and maritime.  Typical indoor worksites where heat-related illnesses may occur include foundries, brick-firing and ceramic plants, glass production facilities, rubber products factories, electrical utilities (particularly boiler rooms), bakeries, confectioneries, commercial kitchens, laundries, food canneries, warehouses without adequate climate control, chemical plants, and smelters.  Outdoor work activities impacted by heat include agriculture, landscaping, construction operations, refining gas/oil and well operations, asbestos and lead removal, waste collection activities, package and mail delivery, and any other activities that require moderate to high physical exertions or the wearing of heavy or /bulky clothing or equipment on a hot day.  Industries with an elevated number of heat-related illness incidents are listed in Attachment 2.

After reviewing relevant local data (including the number of heat-related incidents and fatalities in industries listed in Attachment 2), regions may determine if a regional or local emphasis program is justified.  Region VI has a regional heat emphasis program that has been in effect for several years, CPL 2 02-00-027A,‌enforcement/‌directives/cpl-2-02-00-027a.  Other regions may reference this resource in developing similar programs.  California, Minnesota, and Washington, have state regulations on exposure to hot working conditions and several other states are in rulemaking.  See State Plan links to these standards in Attachment 5.  State Plans without a heat-related illness regulation are encouraged to adopt this heat-related illness enforcement initiative.  Federal agencies should have a heat-related illness prevention plan that includes a system to alert employees, contractors, and temporary workers at their sites to potential heat-related hazards. 

Inspection Procedures and Case File Documentation:  OSHA Area Offices will assess the potential for heat-related illnesses and deaths at both indoor and outdoor worksites where heat-related hazards may exist on heat priority days.  Inspections shall follow the guidance in the Field Operations Manual (FOM) (OSHA Instruction CPL 02-00-164‌directives/cpl-02-00-164), and directives relevant to the focus hazard and other hazards encountered, as well as internal enforcement guidance for Compliance Safety and Health Officers (CSHOs).  The procedures to assess heat conditions and workload are described in the OSHA Technical Manual (OTM), Section III, Chapter 4 - Heat Stress; Chapter 4 - Heat Stress  A review of any potential heat-related hazards should be included in any programmed or unprogrammed inspection on heat priority days.

On expected heat priority days, in an Area Office’s jurisdiction, CSHOs should have cool water and take appropriate precautions to prevent heat-related illnesses.  On those days, enforcement efforts will be increased on heat priority days for the industries listed under the scope section of this memo and in Attachment 2.  Area Directors will:

  • Prioritize inspections of heat-related complaints, referrals, and employer-reported illnesses above processing such activities as phone or /fax investigations where it is possible to initiate an onsite investigation;
  • Instruct CSHOs, during their travels to job sites, to be vigilant of circumstances where employees may be performing moderate or more strenuous work in hot conditions during heat priority days, or working in direct sunlight for extended periods of time, and conduct an intervention (e.g., providing the OSHA heat poster, or wallet cards, discussing the importance of easy access to cool water, cooling areas, and acclimatization) or a self-referral for inspection;
  • Expand the scope of other programmed or unprogrammed inspections to address heat-related hazards where worksite conditions or other evidence (such as employee interviews and OSHA logs) indicates that such hazards may be present.

This approach allows the agency to initiate heat-related assessments at the NWS caution level and to influence employers’ implementation of early interventions to prevent illnesses and deaths among workers who are most at-risk.  OSHA interventions, i.e., having discussions with employers about important steps they can take and providing heat posters and other outreach materials, are critical to mitigating potential hazards and preventing heat-illnesses before they occur.  Inspections should be completed and citations, if any, should be issued expeditiously to facilitate prompt abatement. 

Note:  In cases where it is geographically infeasible to expeditiously initiate an inspection of an unprogrammed activity for heat-related hazards, the Area Office will initiate contact with the employer using non-formal processing to assure a speedy intervention to prevent the potential for heat-related illnesses occurring.

CSHOs can use the OSHA-NIOSH Heat Safety App,, as a resource.  This App provides current and projected heat indices for that day at the current location.  The display indicates the hazard levels as moderate, high, or extreme risk in ranges and offers recommended actions to protect workers.  The NWS provides certified historic weather data to document conditions at the time of an incident and prior days.

During heat-related inspections, CSHOs should;

  • Review OSHA 300 Logs for any entries indicating heat-related illness(es),
  • Review injury and illness reports and obtain any records of emergency room visits and/or ambulance transport, even if hospitalizations did not occur, 
  • Interview workers for reports of headache, dizziness, fainting, dehydration, or other symptoms that may indicate heat-related illnesses,
  • Review employer’s plan to address heat exposure, including acclimatization procedures (especially for new and returning workers), work-rest schedules, access to shade and water (with electrolytes when needed), and any training records associated with implementing a heat illness prevention program,
  • Document, where possible, the heat index on the OSHA-NIOSH Heat App, using the screen save feature on a mobile phone or tablet,
  • Identify conditions and activities relevant to heat-related hazards. These can include, but are not limited to:
    • Potential sources of heat-related illnesses (e.g., working in direct sunlight, a hot vehicle, or areas with hot air, near a gas engine, furnace, boiler or steam lines),
    • WBGT calculations and/or other temperature measurements,
    • Heat advisories, warnings or alerts,
    • The use of heavy or bulky clothing or equipment,
    • The types of activities performed by the employees and whether those activities can be categorized as moderate, heavy or very heavy work,
    • The length of time in which a worker is continuously or repeatedly performing moderate to strenuous activities,
    • Heat-related illnesses among new workers,
    • The presence of any recent vacation time or breaks in employment prior to complaints of heat-related symptoms, and
    • The availability of rest breaks, water and shade on site.

Heat-related inspections should be reported to the regional heat coordinator as soon as possible.  WBGT readings will be in accordance with procedures on conducting WBGT sampling and performing workplace assessments, OSHA Technical Manual, Section III, Chapter 4,  WBGT sampling is considered a more accurate indicator of the effects of heat on individuals than a dry bulb thermometer readings.  Dry bulb readings measure air temperature only.  When appropriate, CSHOs should also conduct workload assessments through direct observation of work practices/operations and employee interviews.  They should particularly note if heavy or bulky clothing or equipment is used.  The information obtained from employer and employee interviews should be verified during the walkaround inspection. 

Area Offices should work with the Regional office to contact the Office of Occupational Medicine and Nursing early in the inspection (especially in fatality or hospitalization cases) to obtain Medical Access Orders, if needed, and for technical assistance.  Contact the Directorate of Enforcement Programs, Office of Health Enforcement, for assistance with enforcement policy.

Citation Guidance:  Any proposed citation for heat-related hazards where the employer’s procedures fail to protect workers from heat-related illnesses are inadequate, will be issued under the General Duty Clause (“GDC”), Section 5(a)(1) of the OSH Act.  Citations for heat-related hazards will be issued for both indoor and outdoor work activities when all elements of a GDC violation are established.  CSHOs should document the relationship between the workplace exposure(s) and the potential for heat-related illness(es), specifically including any and all conditions and activities that present heat-related hazards. 

Ensure that the hazard is clearly described in the citation and avoid solely describing an employer’s failure to implement specific heat stress abatement measures.  The Regional Solicitor's office will be consulted prior to issuing any heat- related 5(a)(1) citations.  A sample Alleged Violation Description (AVD) for a heat-related illness 5(a)(1) violation is located in Attachment 3.  A Hazard Alert Letter (HAL) may be sent when all the elements of a GDC violation are not present.  A sample Hazard Alert Letter (HAL) is located in Attachment 4.  

Several OSHA standards may also be applicable to address certain aspects of worker protection in hot environments including, but not limited to, use of personal protective equipment, sanitation, medical services and first aid, and recordkeeping.

  • The Recordkeeping regulation at 29 CFR §1904.7(b)(5) requires that employers record certain work-related injuries and illnesses.  If a worker requires medical treatment beyond first aid, the worker's illness or injury must be recorded.  However, if a worker merely requires first aid treatment for the worker's condition, the employer is not required to record the condition.  For example, if a worker becomes unconscious, the worker's condition must be recorded.  However, if a worker is only instructed to drink fluids for relief of heat stress, the worker's condition is not recordable.  Refer to 29 CFR §1904.7(b)(5) for an explanation of the difference between medical treatment and first aid.  Recordkeeping issues must be handled in accordance with OSHA Instruction, CPL 02-00-135.
  • The Sanitation standards at 29 CFR §1910.141, 29 CFR §1915.88, 29 CFR §1917.127, 29 CFR §1918.95, 29 CFR §1926.51, and 29 CFR §1928.110 require employers to provide potable water.
  • The general construction safety training and education standard for construction at 29 CFR §1926.21 and 29 CFR §1926.20 requiring a Safety and Health Program as well as frequent and regular safety and health inspections.

Note:  Issuance of citations or HALs should be expedited so abatements can be implemented and achieved earlier to protect other employees exposed to the hazard. 

Other Hazards:  In addition to the focus on hot working conditions, any plain view hazards as described in the FOM (OSHA Instruction, CPL 02-00-164, should be included in the investigation if they come to the attention of the compliance officer.  The scope of the inspection may be expanded to include those hazards.

Outreach, Compliance Assistance, and Training:  The agency will continue its compliance assistance and outreach efforts to educate employers and employees about the dangers posed by hot conditions.  The National Office has provided additional information such as compliance assistance tools to support outreach, and training of CSHOs and compliance assistance specialists (CAS) to address technical issues related to heat illness.  A number of useful resources are currently available on OSHA’s webpage for the Heat Illness Prevention Campaign,, and for OSHA Safety and Health Topics on Heat,  Among other information, these webpages offer resources to help employers assess conditions that may cause or contribute to a heat illness.  These, and additional references, are located in Attachment 5

OSHA Information System (OIS): All enforcement activities (inspections and unprogrammed activities) involving heat-related illnesses must be coded in OIS, Type: N, ID: 02 Value as either "HEATCON" (construction), "HEATGI" (general industry), "HEATMI" (maritime), or "HEATAG" (agriculture), respectively.  Heat-related 5(a)(1) citations and HALs should be identified with the General Duty Key Word “Heat” in OIS.  For related compliance assistance activities (e.g., interventions and outreach) where heat-related illness is addressed, please select “Heat” from the Topics drop-down list.

This policy is effective as of the date of this memorandum.  If you have questions, please contact the Office of Health Enforcement at 202-693-2190.


Attachment 1, Description of serious heat illnesses and common symptoms
Attachment 2, Industries with a high number of heat illness cases
Attachment 3, Sample AVD
Attachment 4, Sample Heat-Related HAL
Attachment 5, Heat-Related Illness Resources


cc:       DCSP

Attachment 1 - Description of serious heat-related illnesses and common symptoms

Attachment 1 - Description of serious heat-related illnesses and common symptoms
Serious Heat- Related Illnesses Include But Are Not Limited To Symptoms and Signs
Heat stroke
  • Confusion
  • Slurred speech
  • Unconsciousness
  • Seizures
  • Heavy sweating or hot, dry skin
  • Very high body temperature
  • Rapid heart rate
Heat exhaustion
  • Fatigue
  • Irritability
  • Thirst
  • Nausea or vomiting
  • Dizziness or lightheadedness
  • Heavy sweating
  • Elevated body temperature or fast heart rate
Heat cramps
  • Muscle spasms or pain
  • Usually in legs, arms, or trunk
Heat syncope
  • Fainting
  • Dizziness
Heat rash
  • Clusters of red bumps on skin
  • Often appears on neck, upper chest, and skin folds
Rhabdomyolysis (muscle breakdown)
  • Muscle pain
  • Dark urine or reduced urine output
  • Weakness
Acute kidney injury (AKI)
  • Kidneys become damaged due to inadequate blood flow or a second mechanism is rhabdomyolysis of kidney muscle tissue.
  • Diagnosed by elevated blood creatinine levels. Urine output is also reduced.
  • May lead to kidney failure

Attachment 2 - Industries with a high number of heat-related illness cases and fatalities

Bureau of Labor Statistics for years from 2011 to 2019

According to BLS, the industries with the highest average fatalities per year are the following:

Bureau of Labor Statistics for years from 2011 to 2019
Industry NAICS Average fatality cases 2011-2019 Average cases with days away
Agriculture, forestry, fishing and hunting 11XXXX 5 113
Mining 21XXXX 1 80
Construction 23XXXX 13 567
Manufacturing 31XXXX-
4 426
Administrative and support and waste management and remediation services, landscaping 561XXX 6 306
Transportation and warehousing 48XXXX-
4 297

OSHA Information Systems (OIS) Reports for 2015 to 2020 (excludes State Plans)

OSHA Information Systems (OIS) Reports for 2015 to 2020 (excludes State Plans)
Industry NAICS Avg OSHA inspections
Fatality/Catastrophe OSHA Heat Inspections
USPS 491110 13 1 / 0
Commercial and Institutional Building Construction 236220 7 0 / 0
Temporary Help Services 561320 5 0 / 0
Landscaping Services 561730 4 0 / 2
Highway, Street, and Bridge Construction 237310 3 0 / 0
Couriers and Express Delivery Services 492110 2 0 / 0
Support Activities for Oil and Gas Operations 213112 2 0 / 0
Solid Waste Collection 562111 2 1 / 1
All Other Specialty Trade Contractors 238990 2 0 / 2
Commercial Bakeries 311812 2 0 / 1
Other Heavy and Civil Engineering Construction 237990 1 0 / 1
Industrial Building Construction 236210 1 0 / 1
Water and Sewer Line and Related Structures Construction 237110 NA 0 / 1
Farm Labor Contractors and Crew Leaders 115115 NA 1 / 0
Sheet Metal Work Manufacturing 332322 NA 1 / 0
Specialized Freight (except Used Goods) 484220 NA 1 / 0
Local Messengers and Local Delivery 492210 NA 1 / 0
Offices of Mental Health Practitioners (except Physicians) 621330 NA 1 / 0
Commercial and Industrial Machinery and Equipment (except Automotive and Electronic) Repair and Maintenance 811310 NA 1 / 0
Strawberry Farming 111333 NA 0 / 1
Tobacco Farming 111910 NA 0 / 1
Reconstituted Wood Product Manufacturing 321219 NA 0 / 1
Other Motor Vehicle Parts Manufacturing 336390 NA 0 / 1
Other Waste Collection 562119 NA 0 / 1
Marinas 713930 NA 0 / 1
National Security 928110 NA 0 / 1

Severe Injury Reports for 2015 to 2020 (excludes State Plans)

Severe Injury Reports for 2015 to 2020 (excludes State Plans)
Industry NAICS Avg SIR reports per year 2015-2020
USPS 491110 24
Couriers and Express Delivery Services 492110 12
Landscaping Services 561730 8
Highway, Street, and Bridge Construction 237310 8
Commercial and Institutional Building Construction 236220 7
Support Activities for Oil and Gas Operations 213112 6
Roofing Contractors 238160 6
Solid Waste Collection 562111 6
Temporary Help Services 561320 6

Attachment 3 - Sample Heat-Related AVD

The 5(a)(1) AVD language for heat-related hazard violations of Section 5(a)(1) must specify the heat-related hazard, such as all sources of heat (e.g., environmental temperature measurements and information on heat-generating equipment), including any specific workplace conditions or practices making exposed employees vulnerable to a likelihood of heat-related illnesses (e.g., performing moderate to very heavy roofing work, dumping heavy refuse bins while running behind a sanitation truck, wearing impermeable protective clothing, and lack of acclimatization of new or returning workers), as applicable. The alleged heat-related hazard descriptions should not include the employer's failure to implement any specific abatement measures, such as acclimatizing workers to the heat; or failure to provide drinking water, shade, and air conditioning; or training workers on heat stress.

Example AVD:
On or about and at times prior to [the date of the incident], employees were exposed to the recognized hazard of high ambient heat from [list sources of and conditions of ambient heat, such as direct sun, boiler, steam, furnace, combustion engine] during the performance of their job duties, including [describe specific task(s)].  [Describe temperature, relative humidity, WBGT measurements and calculations, and any aggravating factors such as heavy or bulky clothing, duration of exposure, direct sunlight, and level of workload. Include any NOAA heat advisory or alert that supports a high ambient hazardous heat conditions and WBGT if known]. Such exposures are likely to lead to the development of serious heat-related illnesses such as, but not limited to, heat cramps, heat stress, heat exhaustion, and heat stroke.  [Describe any heat-related incidents/illnesses that occurred].

Where the information is available and applicable to the inspection, the case file should document factors such as the employer’s knowledge of the hazard, the reading on the OSHA-NIOSH App (use the camera screen shot function to save the image of the reading, when possible), WBGT temperature if possible, wind speed and /direction, radiant heat, cloud cover, length of time the work was performed, and other sources of heat in the workplace.  Additionally, document whether any exposed employees were temporary workers, new hires, or employees returning from prolonged leave periods who were not acclimatized. 

When listing availability of feasible abatement methods in the citation, document all potential measures the employer failed to implement that would have materially reduced or eliminated the hazard of heat-related illness, such as providing cool, drinking water, frequent rest breaks, cooling or shaded areas, and access to first aid/prompt medical attention. NOTE: Do not set forth recommended measures as alternative options.  Use language such as "Among other methods, feasible and acceptable measures to abate this hazard may include:" At the end of listing the proposed measures, insert the following:  “The listing of these available abatement methods does not necessarily mean that any one measure is sufficient to abate the hazard”.

Any water or other fluids provided by the employer should be cool, and provided in a location that is familiar to the employees, near the work, easy to access, and in sufficient quantity for the duration of the work.

Attachment 4 - Sample HAL

Note: This letter must be adapted to the specific circumstances noted in each inspection.  The letter below is an example of the type of letter that may be appropriate in some circumstances.  If the employer has implemented, or is in the process of implementing, efforts to address hazardous heat conditions, those efforts should be recognized and encouraged, where appropriate.  CSHOs should tailor the recommended controls outlined below to the specific needs of the employer.  Italicized and bracketed text are for OSHA compliance use only and should not be included in the letter.

Dear Employer:

An inspection of your workplace and evaluation of your OSHA recordkeeping logs at [location] on [date] disclosed the following workplace condition(s) which have been associated with the development of heat-related illnesses in workers:

[Describe the work performed for each task or job, including the type of PPE worn, the source of heat, WBGT and duration of the heat exposure, reading on the OSHA-NIOSH heat app during the inspection, any heat notifications from the National Weather Service, and any other information relevant to workers' exposure to the risk of heat-related illness].

In the interest of workplace safety and health, I recommend that you voluntarily take the necessary steps to materially reduce or eliminate your workers' exposure to the conditions listed above, including, but not limited to, the following:

General Controls:
General controls include training, personal protective equipment (PPE), administrative controls, health screening, and heat alert programs.

  1. Training: inform workers of the following (Modify this list as appropriate for the specific situation):
    1. Hazards of heat-related illnesses.
    2. How to avoid heat-related illnesses by recognizing and avoiding situations that can lead to heat-related illnesses. 
    3. Recognition of signs and symptoms of heat-related illnesses.
    4. First-aid procedures.
    5. Employer's program to address heat-related illnesses.
  2. Personal Protective Clothing and Equipment:  (CSHOs should recommend the appropriate PPE).
    1. Hats for work outdoors in the sun.
    2. For indoor work, loosely worn reflective clothing to deflect radiant heat, such as vests, aprons or jackets.
    3. Cooling vests and water-cooled/dampened garments may be effective under high temperature and low humidity conditions.  However, be aware that cooling vests can become an insulator when they reach the body's temperature.
    4. In environments where respirator usage is necessary, consult with an industrial hygienist to determine the appropriate clothing to prevent heat stress while still protecting the workers.
    5. Consider the use of dermal patches for monitoring core temperature to better identify when workers need to be removed from the work area.
    6. Consider the use of heart rate monitoring to better identify when workers need to be removed from the work area.,  Both sustained (180 minus age) and recovery (120 bpm after a peak work effort) heart rates are recommended guidelines for limiting heat strain. ​​​​​​
  3. Administrative Controls: (CSHOs should consult the OSHA Technical Manual, Section IIL Chapter 4 for additional information).
    1. Schedule hot jobs for cooler parts of the work day, and routine maintenance and repair work should be scheduled for the cooler seasons of the year when possible.
    2. Provide adequate cool drinking water on the worksite that is easily accessible and permit employees to take frequent rest and water breaks.
    3. Use relief workers and reduce physical demands of the job.
    4. Have air-conditioned or shaded areas available for water breaks and rest periods.
  4. Health Screening and Acclimatization:
    1. New workers should be allowed to get used to hot working environments by using a staggered approach over 7-14 days.  For example, begin work with 50% of the normal workload and time spent in the hot environment, and then gradually increase the time over a 7-14 day period.  The same should be done for workers returning from an absence of three or more days, staging acclimatization over 3 consecutive days.
      1. Workers should be made aware of the following:
        Medications such as the following can increase risk of heat stress:
        • Amphetamines – sometimes prescribed for narcolepsy or attention deficit hyperactivity disorder (ADHD),
        • Diuretics - water pills,
        • Antihypertensives - blood pressure medication,
        • Anticholinergics - for treatment of chronic obstructive pulmonary disease (COPD), and
        • Antihistamines - allergy medications
      2. Dangers of using illegal drugs and alcohol in hot work environments. Illegal amphetamines such as methamphetamine are particularly hazardous when heat stress is present.
      3. Some conditions, such as pregnancy, fever, gastrointestinal illness, heart disease, and obesity, may increase the risk of heat-related illness.  Workers should be advised to check with their doctors if they have any questions. (Please note: the employer is NOT entitled to know whether workers have these conditions, but only whether workers have any health conditions that limits their ability to perform their job duties.  In some instances, workers with chronic conditions may need extra time to become acclimatized or may need other accommodations, such as more frequent breaks or restricted work.)
      4. Workers should consult a doctor or pharmacist if they have questions about whether they are at increased risk for heat-related illness because of health conditions they have and/or medications they take. 

You may voluntarily provide this Area Office with progress reports on your efforts to address these heat-related conditions in your workplace.  OSHA may return to your worksite to further examine the conditions noted above.



Area Director


Attachment 5 - Heat-Related Illness Resources

OSHA’s Heat Illness Prevention Campaign,
OSHA Safety Topics Heat,
OSHA Technical Manual (OTM), Section III, Chapter 4 - Heat Stress; Chapter 4 - Heat Stress 

State Plans with Heat Standards


[1] For resources discussing heat-related illnesses and common symptoms, see NIOSH Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments DHHS (NIOSH) Publication Number 2016-106, February 2016,

[2] WBGT is similar to the heat index, but in addition to air temperature and humidity, WBGT adds the radiant effects of the sun (or other heat source).  Both NIOSH and ACGIH guidelines use WBGT to assess the heat-related hazard. 

[3] For resources discussing the heat-related hazards of temperatures reaching 80℉ or above, see
Maung Z, Tustin AW. The heat death line: proposed Heat Index alert threshold for preventing heat-related fatalities in the civilian workforce. New Solut. 2020;30(2):138-145,

Arbury S, Jacklitsch B, Farquah O, Hodgson M, Lamson G, Martin H, Profitt A,  Heat Illness and Death Among Workers — United States, 2012–2013, Morbidity and Mortality Weekly Report (MMWR), August 8, 2014 / 63(31);661-665,