Stanford University

Outdoor Heat Illness Prevention

Working in hot outdoor environments can result in heat illness. If left untreated, heat illness can rapidly lead to serious health-threatening situations.

To prevent heat illness, Stanford personnel, including field researchers, grounds and facility maintenance staff, and their supervisors, must:

  • Understand the environmental and personal risk factors for heat illness
  • Take the necessary preventative steps
  • Recognize the early signs and symptoms of heat illness
  • Know the University’s established emergency response procedures for heat illness

Basics of heat illness

Heat illness signs and symptoms

Early signs and symptoms of heat illness include:

  • Dehydration
  • Headache
  • Muscle cramps
  • Unusual fatigue

Heat illness may progress quickly to more serious illness (e.g. heat exhaustion and heat stroke). Symptoms include:

  • Cool, moist skin
  • Dizziness or lightheadedness
  • Nausea or vomiting
  • Fast heartbeat
  • Confusion or unusual behavior
  • Excessive sweating or red, hot, dry skin and face
  • Convulsions or seizures
  • Fainting

If you notice signs or symptoms of heat illness, give first aid immediately, or follow emergency procedures. People with symptoms must not be sent home or left unattended without medical evaluation.

Environmental risk factors

The main environmental risk factors for heat illness are:

  • Air temperature
  • Relative humidity
  • Radiant/conductive heat (from the sun and ground)
  • Air movement (safe when cooler than 95 degrees Fahrenheit)
  • Work intensity or duration
  • Clothing worn

Personal risk factors

The main personal risk factors for heat illness are:

  • Age
  • Degree of acclimatization
  • Medical conditions or use of prescription medicines (consult with personal physician)
  • Water consumption
  • Alcohol consumption
  • Caffeine consumption

Workplace emergency procedures

If any symptoms of serious illness are present, and trained personnel are not immediately available to make an assessment, call 911 immediately (9-911 from a campus phone) or transport the employee to the Stanford Hospital Emergency Room. While waiting for emergency help:

  • Get the person to a cool environment.
  • Loosen or remove excess clothing.
  • If the person is conscious and not nauseous, provide cool drinking water.
  • Fan and mist the person with water.
  • Apply a water-soaked towel (or an ice pack wrapped in a towel) to the head. Apply ice packs to the armpits.

Any employee who is evaluated for heat illness in the emergency room must follow-up with the Stanford University Occupational Health Center at (650) 725-5308 on the next business day. The employee must be medically cleared before returning to work.

Preventing heat illness: general requirements

Supervisors shall ensure that specific measures are taken (see below) to prevent heat illness amongst their staff. Supervisors shall comply with Cal/OSHA’s regulatory requirements (Title 8 CCR 3395).

Employees and supervisors shall be trained before beginning outside work in warmer weather. This safety training shall cover:

  • Heat Illness Prevention Plan and Training:
    • This training includes the general information in this document, along with department-specific procedures. Departments shall document local heat illness prevention procedures, which shall be made available to employees. Refer to Heat Illness Prevention Procedures and Training or contact EH&S at (650) 723-0448 for guidance on creating these procedures.
    • Supplemental training materials can be found online. The training shall be documented (refer to Heat Illness Prevention Procedures and Training). Contact EH&S for additional assistance.
  • A sufficient quantity of fresh and suitably cool drinking water shall be readily accessible to allow every working person to drink at least four cups per hour. Personnel shall be encouraged to maintain regular fluid intake.
  • Prior to assigning outdoor work during warm periods, check weather forecasts and the current weather to assess the potential for heat stress or illness. Note that for unseasonably humid days, the heat load will be greater. For warmer periods, and especially during worker acclimatization:
    • Schedule outdoor work during cooler parts of the day.
    • Plan a staff rotation for strenuous work tasks.
    • Advise staff to wear lighter, loose-fitting clothing and wide-brimmed hats.
  • The body needs a certain period of time to adjust to working in heat and humidity, especially when heavy physical exertion is required. Typically, people can adapt to significant increases in heat within four to 14 days of a progressively increasing workload. Note that acclimatization is required for all staff during a heatwave, and for new or recently returning employees who will work outdoors at 95 degrees Fahrenheit or warmer.
  • For outdoor temperatures of 80 degrees Fahrenheit or warmer:
    • Supervisors shall ensure that adequate shade is present at or near the work area for employees to take their rest/meal breaks.
    • Supervisors must encourage employees to take a preventative cool-down rest in the shade when they feel it is needed to prevent overheating. Workers taking a cool-down rest shall:
      • Be monitored for heat illness symptoms
      • Take at least five minutes to rest in the shade
      • Not be ordered back to work until any signs or symptoms of heat illness are gone
    • Supervisors shall provide an effective means for personnel to contact the supervisor and emergency services (e.g. cell phones or walkie-talkies).
  • For outdoor temperatures of 95 degrees Fahrenheit or warmer, supervisors shall also:
    • Monitor employees for alertness and signs or symptoms of heat illness (either by direct supervision, a buddy system, phone or radio communication, or other means).
    • Remind employees to drink plenty of water throughout the workday.
    • Hold daily pre-shift meetings to remind workers of the required monitoring described above, including the need to drink plenty of water and the right to take cool-down rest breaks as needed.

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