Outdoor Heat Exposure – Frequently Asked Questions (OHE-FAQs)

Outdoor Heat Exposure topic page

Scope and Purpose


Q: How do you distinguish between double-layer and vapor barrier clothing?

A: Vapor barrier clothing does not allow sweat to evaporate from the body or air to reach the skin. Double-layer clothing inhibits but still allows sweat to evaporate and air to reach the skin.


Q: What category does Tyvek fit under?

A: Standard Tyvek would fall under the second category of outdoor temperature action levels.

Rain wear

Q: What category does rain wear fit under?

A: Rain wear would fall under the second category of outdoor temperature action levels.

Personal clothing

Q: If a person has on several layers of clothes, where does that fall in the table?

A: Wearing several layers of clothes would fall under the second category of outdoor temperature action levels.

Q: What about a flannel shirt over a tee shirt?

A: This would be considered general work clothing and fall under the first temperature action level of 89 degrees Fahrenheit.

Q: What about coveralls with a T-shirt under, or coveralls with just underclothes under them?

A: This would be considered general work clothing and fall under the first temperature action level of 89 degrees Fahrenheit.

Traffic Vest

Q: Where does a traffic vest fall in under the new rule?

A: This would be considered general work clothing and fall under the first temperature action level of 89 degrees Fahrenheit.

Abrasive Blasting Hood

Q:  Does the 77°F action level apply to an employee performing outdoor abrasive blasting while wearing a respirator with a shroud?

A:  A head shroud significantly impedes body heat loss acting in the same manner as double layer clothing; as such the 77°F action level would apply.   However, if the respirator  has a cooling vortex, then it would fall under the  89°F  action level.

Normally coveralls would be worn during abrasive blasting which would be considered double layer clothing, placing the employee at the 77°F action level, regardless if the respirator  had a cooling vortex or not.

Work environment

Q: Is it considered to be outdoor work when working in a manhole, underground utility vault, an enclosed space, or tunnel?

A: Work performed within outdoor containment areas such as on lead removal projects on bridges, or where an employee must enter a manhole, tunnel, or outdoor vault are considered “outdoor” work activities for purposes of the outdoor heat exposure rule.


Q: What about employees that drive vehicles for their job?

A: Employees occupying transportation road vehicles, such as delivery vans, trucks or other vehicles, are not considered to be “working outdoors” while driving or occupying the vehicles if the vehicles are able to maintain airflow throughout the vehicle by use of fans, vents, open windows, etc.

Q: What about a employees who work in the back of an armored car?

A: If there is no airflow from fans, vents, windows, or air conditioning, it is considered to be outdoor heat exposure.

Q: What about a truck driver who is loading and unloading outdoors for about 30 minutes at a time?

A: If the worker is out of the vehicle (outdoors) for more than 15 minutes in an hour, then they would be covered by the outdoor heat exposure standard during that time.


Q: What if an employee is only outdoors for a short time, and then moves to air conditioning?

A: The outdoor heat exposure standard does not apply to incidental exposure which exists when an employee is not required to perform a work activity outdoors for more than fifteen minutes in any sixty-minute period. This exception may be applied every hour during the work shift.

Q: Is the 15 minute exposure consecutive?

A: No it is not.

Q: What if the trigger temperature doesn’t happen until late afternoon?

A: The outdoor heat exposure standard does not apply until one of the temperature action levels in Table 1 is met.


Q: Can the cab of an air conditioned truck be considered an engineering control?

A: Yes

Q: Would a work shack be considered indoors if machinery is also kept there?

A: The structure is considered to be an outdoor environment until four outside walls and a roof are erected.

Employer/Employee Responsibility

Q: What is the source to rely on to tell the outside temperature?

A: The temperature must be determined directly in the work areas and the employer may not rely solely on the weather report.

Q: Are employers responsible for supplying water even though employees bring their own?

A: Yes, the employer is to ensure that there is adequate water available and that each employee has the opportunity to drink at least a quart of water an hour while the outdoor heat exposure standard applies.

Drinking Water

Water suitability

Q: Is an onsite garden hose acceptable to drink out of or fill containers? If not, why not?

A: An onsite garden hose is not acceptable because it may be contaminated.

Q: What about an outside faucet on a neighboring building or house on a construction site?

A: An outside faucet (hose bib) that provides potable water may be used to fill water containers, however employees should not drink directly from it.

Q: Does the drinking water need to be a certain temperature range?

A: The outdoor heat exposure standard does not require water to be at a certain temperature. However water of 50-60 degrees Fahrenheit is recommended.

Q: What if water sits in a truck cab all day?

A: If the water is too hot, and employees do not wish to drink it, it is not considered to be suitable.

Water location

Q: If you have a multi-employer commercial site, would it be okay if water is kept in a common place- i.e. a work trailer?

A: Yes, as long as it is readily accessible.

Q: What about employees that can’t leave their stations (i.e. paving crew, flaggers, lead containment areas, etc.)?

A: Under these circumstances you may need to provide extra water breaks or individual water containers so that employees can keep water with them at all times.

Q: How would you expect employees that have to travel from location to location to get water?

A: Employees must be able to stop to buy water or carry sufficient quantities with them.

Q: Can an employee go into a neighboring building to get water?

A: Yes, they may as long as the building is within a reasonable distance.

Q: Does “readily accessible” mean as long as they can walk somewhere close by to get water?

A: Yes

Q: If sub contractors have no water in their work trucks, can they go to the general contractor to get water?

A: Yes, but it is the direct employer’s responsibility to ensure that proper amounts of water are available.

Q: Is the general contractor responsible for providing water to the subs?

A: No, but they may if they wish.

Q: If sufficient water is not on a construction site, would a citation be given to the general or the sub contractor?

A: The sub contractor is responsible for their direct employees and can be cited and the general contractor may be cited under Stute, depending on circumstances.

Q: Are individual drinking cups required?

A: Yes individual cups or containers are required.

Q: What if an employee refuses to drink water? What are the options for the employer?

A: The employer is to provide the water and encourage employees to drink the water. They cannot force an employee to drink the water.

Q: What is defined as sufficient amounts of water?

A: This means that water is always available to all employees.

Responding to signs and symptoms of HRI

Q: What if there is no phone service where work is being done and an employee has heat illness issues?

A: Employers must address heat illness in the same manner as any other work-related illness or injury, so other provisions such as radios should be employed.

Q: Are misting stations okay to have?

A: They are allowed but not required.

Q: Is a cooling vest acceptable?

A: They are allowed but not required.

Information and training

Q: What are the effects of medications in warm weather?

A: Employees should be encouraged to consult with their health care provider if they have any questions about their medications or health status.

Q: What if an employee brings their own caffeinated beverage?

A: This is not prohibited but the employer must encourage employees to consume water or other suitable beverages to ensure proper hydration.

Q: Can an employer print off the heat stress information off the L&I website and show it at a safety meeting? Does that constitute proper training?

A: Yes, as long as the training also includes specific procedures for that particular employer including providing water and responding to signs and symptoms of heat-related illness.

Q: What about employees provided by subcontractors that do not speak English? Example: Russian

A: Training must be given in a language that the employee understands.

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