Chapter 40

HEAT STRESS HAZARD ASSESSMENT AND CONTROL

Contents

Approved by Dan Best
NEW 07/12

40.1 Policy
40.2 Scope
40.3 Applicability
40.4 Exceptions
40.5 Roles and Responsibilities
40.6 Definitions
40.7 Required Work Processes
Work Process A. General Requirements
Work Process B. Control of Heat Stress
Work Process C. Heat Stress Screening Threshold
Work Process D. Heat Stress Emergencies
40.8 Source Requirements

NOTE:
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40.1 Policy

Berkeley Lab’s Heat Stress Policy addresses the hazards of heat stress at the Laboratory site by:

40.2 Scope

This policy applies to all Berkeley Lab employees; casual and participating visitors; affiliates; and subcontractors.

40.3 Applicability

This policy describes how the heat stress policy at Berkeley Lab meets all federal, state, and Department of Energy (DOE) guidelines as well as recognized good practice.

40.4 Exceptions

       None

40.5 Roles and Responsibilities

Role

Responsibilities

All Berkeley Lab Supervisors and Building Managers

  • Arranging first aid training for workers
  • Monitoring the workplace to determine when hot conditions arise
  • Whenever possible, scheduling hot jobs for the cooler part of the day
  • Ensuring that workers are drinking enough water
  • Adjusting work practices as necessary when workers experience heat stress
  • Making adjustments for workers who must wear personal protective clothing and equipment that retains heat and restricts the evaporation of sweat

Workers

  • Following instructions and training for controlling heat stress
  • Recognizing the potential for heat stress in the work environment
  • Being alert to symptoms in yourself and others
  • Avoiding consumption of excessive caffeine, which can contribute to heat stress
  • Drinking small amounts of water regularly to avoid dehydration
  • Using PPE appropriately

Facilities Division Project and Construction Managers

  • Issuing "stop work" notices to contractors in non-compliance with the LBNL heat stress program. Providing fans and other means to increase airflow or ventilation in hot work areas
  • Auditing work performed by contractors to ensure compliance. Informing the Inspection Groups of non-compliance

Industrial Hygiene Group

  • Providing project-specific guidance and recommendations
  • Helping Managers to determine an appropriate work/rest regime for workers

40.6 Definitions

Term

Definition

Action Level

Level of concern where a corrective action is taken

Contractor

A contractor employed by Berkeley Lab.  Both the contractor and the work crew will be non-LNBL employees.

PPE

Personal Protective Equipment.  Safety equipment worn by employees; may include safety glasses, respirators, coveralls, gloves, etc.

Thermal Radiation

Transfer of heat from hot objects through air to the body. Working around heat sources such as furnaces will increase heat stress. Additionally, working in direct sunlight can substantially increase heat stress.

High Humidity

Under conditions of high humidity, the rate of evaporation of sweat from the skin decreases. If air temperature is as warm as or warmer than the skin during times of high humidity, blood brought to the body’s surface cannot dissipate heat.

Wet Bulb Globe Temperature Index (WBGT)

Measurement is often required of those environmental factors that most nearly correlate with deep body temperature and other physiological responses to heat. At the present time, the Wet Bulb Globe Temperature Index (WBGT) is the most-used technique to measure these environmental factors.


 

40.7 Required Work Processes

Work Process A. General Requirements

  1. Heat Stress Description. Heat stress, the physical stress of hot environments, can be influenced by a combination of factors, such as the type of clothing being worn, physical activity, time spent working, breaks between work activity, medications, and environmental factors such as ambient air temperature, air velocity, and relative humidity. Although the Bay Area generally offers moderate weather conditions, occasionally there may be brief periods of hot weather that can lead to uncomfortable working conditions and, possibly, heat stress for employees. A mild or moderate heat stress (i.e., office environments) may cause discomfort, but it is rarely harmful to health. However, as the heat stress approaches human tolerance limits (e.g., exterior work on hot days), the risk of heat-related disorders increases. This section is intended to provide guidance to line managers and workers on how to recognize and control heat stress in office environments or while working outdoors.
  2. Recognizing Heat Stress. Employee heat complaints provide good cues for the recognition of heat stress in the workplace. Supervisors are encouraged to obtain feedback from employees on their working conditions during periods of hot weather. Methods for obtaining this input may include visiting assigned spaces, calling employees in areas known to be warm, or questioning employees during safety and group meetings. For additional information and training on heat stress and other outdoor hazards, contact Health Services at ext. 6266.

Work Process B. Control of Heat Stress

Self-awareness is one of the key steps to reducing heat-related disorders. Employees and supervisors should terminate exposure to heat stress at the onset of the first symptoms. Supervisors should consider a worker’s physical condition when determining heat stress conditions. Obesity, lack of conditioning, medical conditions, use of medications, pregnancy, and inadequate rest can increase susceptibility to heat stress even in indoor office environments. Additional industrial-hygiene practices and administrative and engineering controls are listed below:

  1. Wear lightweight, light-colored, loose clothing that allows free movement of cool dry air over the skin’s surface to allow the removal of heat from the body by evaporation. Evaporation of sweat from the skin is the body’s predominant heat removal system.
  2. Drink plenty of chilled hydrating fluids such as water or commercial hydrating fluids to prevent dehydration. Since thirst is not a sufficient indicator of fluid replacement, workers are encouraged to drink about 1 cup of cool water every 15 to 20 minutes during heat stress conditions.
  3. To increase evaporation and cooling of the skin, use general ventilation or fans for spot cooling.
  4. Work demands should be made lighter by taking frequent breaks in a cooler area, completing them over a longer time period, and setting the work pace with the least heat-tolerant worker in mind.
  5. Heavy workloads should be scheduled during cooler times of the day (i.e., early morning).
  6. Wearing personal protective equipment (PPE) during hot weather can dramatically increase an individual’s heat stress level. Non-breathing fabrics like Tyvek do not allow for the evaporation of sweat. The use of respirators also adds an additional physiological burden, increasing heat stress levels. Tasks requiring these types of PPE should be postponed when feasible. If the work must be performed, then an effective work-rest cycle must be established. The Industrial Hygiene Group must be contacted prior to beginning this type of work.
  7. A light, cool lunch is recommended during hot days, instead of a heavy meal. Heavy meals can reduce your ability to release heat because blood flow is redirected to the stomach instead of to the skin for cooling.
  8. Employees should report to Health Services if they feel they are suffering from the onset of a heat-related disorder. In emergency situations, contact the Fire Department by calling ext. 7911.

Work Process C. Heat Stress Screening Threshold

  1. The table below is used as a screening tool by health and safety professionals to determine the environmental contribution to heat stress in outdoor environments. The temperatures listed in this table take into consideration air temperature, radiant heat, and humidity (wet bulb globe temperature [WBGT] Index °C). The Industrial Hygiene Group is available to measure WBGT; however, when indoor air temperatures exceed 85 °F (29.5 °C), supervisors are responsible for exercising their judgment in modifying employees’ work schedules, workloads, etc.
  2.  

    Acclimatized Worker
    (WBGT values in °C)

    Unacclimatized Worker
    (WBGT values in °C)

    Work demand*

    Light

    Moderate

    Heavy

    Very Heavy

    Light

    Moderate

    Heavy

    Very Heavy

    100% work

    29.5

    27.5

    26

     

    27.5

    25

    22.5

     

    75% work; 25% rest

    30.5

    28.5

    27.5

     

    29

    26.5

    24.5

     

    50% work; 50% rest

    31.5

    29.5

    28.5

    27.5

    30

    28

    26.5

    25

    25% work; 75% rest

    32.5

    31

    30

    29.5

    31

    29

    28

    26.5

    *Work demand examples:
    Light – Sitting with moderate arm and leg movements.
    Moderate – Walking about with moderate lifting or pushing.
    Heavy – Heavy assembly work on a noncontinuous basis.
    Very heavy – Shoveling wet sand.

  3. When interior temperatures fall outside the recommended guidance range of 65 °F to 85 °F, division directors, unit heads, and supervisors should use their discretion in modifying employee work assignments, including changes in location, changes in time of beginning or end of workday, sharing duties, etc. Line managers should consider employee medical and physical conditions when applying this temperature range as a guideline.
  4. For employees working outside, modifications to employee work assignments should be considered when the ambient temperature exceeds 85 °F. More frequent rest periods may be required in addition to the strategies listed above. Consideration must also be given to the increased heat stress levels caused by wearing certain types of personal protective equipment (PPE).
  5. If temperature extremes effectively prevent an employee from performing his or her work, and alternate assignments and on-site work locations appropriate to the employee’s job classification are not available, line managers should use their judgment in allowing their affected employees to work at home for the period during which the employee’s work cannot be performed on site. EH&S neither requires nor authorizes changes in employee work assignments under extreme temperature conditions; these decisions rest with line management.

Work Process D. Heat Stress Emergencies

Heat-related disorders can be caused by prolonged periods of heat stress. Listed below are some common heat-related disorders, including their symptoms:

  1. Heat Exhaustion. Heat exhaustion occurs when your body’s ability to regulate temperature is overwhelmed but not completely broken down.
    1. Symptoms of heat exhaustion include:
      1. Clammy, cool, moist, and pale skin
      2. Fatigue or weakness
      3. Heavy perspiration
      4. Intense thirst from dehydration
      5. Low to normal blood pressure
      6. Anxiety or agitation
      7. Clouded senses or impaired judgment
      8. Fainting or loss of coordination
      9. Loss of appetite
      10. Nausea or vomiting
      11. Rapid breathing
      12. Slightly low oral temperature
    2. Immediate response actions for heat exhaustion are as follows:
      1. Call the Fire Department immediately (ext. 7911)
      2. Move the victim into the shade or a cooler area
      3. Loosen the victim’s clothing and shoes for evaporative cooling
      4. Fan the victim
      5. Elevate the victim’s legs
      6. Give the victim water
      7. Cool the victim with damp, cool towels
      8. Stay until medical help arrives
  2. Heatstroke is the most severe of the heat-related disorders. Heatstroke is a life-threatening emergency that requires immediate medical attention. Heatstroke is more likely to occur in outdoor work.
    1. Symptoms of heatstroke include:
      1. No perspiration on skin
      2. Hot, red, or flushed skin
      3. High body temperature, 105 °F or above
      4. Rapid pulse
      5. Difficulty breathing
      6. Constricted pupils
      7. High blood pressure
      8. Headache or dizziness
      9. Confusion or disorientation
      10. Weakness
      11. Nausea or vomiting
      12. Seizures
    2. Immediate response actions for heatstroke are as follows:
      1. Call the Fire Department immediately (ext. 7911).
      2. Lower the victim’s body temperature as quickly as possible. Applying damp, cool towels, or ice packs to armpits, elbows, wrists, or backs of knees may help.
      3. Stay with the victim until medical help arrives.

40.8 Source Requirements

 

 

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