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ES&H Manual
Chapter 6670 Thermal Stress
Jefferson Lab defines thermal stress as the physical and physiological reactions of a worker to temperatures that fall outside the normal comfort zone. The potential for heat and cold stress at Jefferson Lab exists mainly during the summer and winter months.

Mitigation actions are used to reduce thermal stress hazard conditions. The actions defined within this section meet or exceed the contractual requirements of 10 CFR 851.

Jefferson Lab recognizes that the most effective mitigation technique for thermal stress conditions is to wear appropriate clothing, and personal protective equipment. Work planning at Jefferson Lab, particularly during the summer months, considers ambient temperature and implements mitigation techniques as required.

Jefferson Lab uses the National Weather Service Heat Stress Index for areas exposed to ambient conditions. For temperature monitoring, application guidelines, and calculations, the 2016 Threshold Limit Values for Physical Agents in the Work Environment section on Thermal Stress - Heat Stress & Heat Strain is used (measured as the Wet Bulb Globe Temperature (WBGT)).

This chapter does not address specific hazards or injuries resulting from sudden exposure to cryogenic materials. (See ES&H Manual Chapter 6550 Cryogenic Safety Program.)


T1 Heat Stress Mitigation
Areas of known routine hot working environments for all or part of the year are monitored on a periodic basis. ES&H Manual Chapter 6670 Appendix T1 Heat Stress Mitigation addresses the procedure used to monitor and mitigate potential injury or illness due to heat stress.
T2 Cold Stress Work Cessation Procedure
As of the approval date of this chapter, there are no known work environments with temperatures that would be considered cold stress areas. One area with routine cold conditions is the food refrigeration area of CEBAF Center. However, this area is not occupied for continuous work but only visited as needed. ES&H Manual Chapter 6670 Appendix T2 Cold Stress Work Cessation Procedure addresses the procedure used to mitigate potential injury or illness due to cold stress.

Management responsibility may be delegated to a task qualified Jefferson Lab employee at the discretion of the responsible manager.

Everyone at Jefferson Lab
Industrial Hygiene
  • Monitor anticipated heat conditions and conduct heat stress monitoring.
  • Advise staff when work demand and work/rest regimen is to be implemented.
  • Maintain heat and cold monitoring records in accordance with department procedures.
Facilities Management and Logistics
  • Maintain the on-site Jefferson Lab weather station and provide a link to the data on a Jefferson Lab web page (currently
Supervisor/Subcontracting Officer's Technical Representative (SOTR)/Sponsor
  • Request assistance from Industrial Hygiene to evaluate work assignments involving heat stress conditions.
  • Minimize worker's exposure to heat sources when feasible.
    • Allow for acclimatization in work plan when elimination of heat stress conditions is not feasible.
  • Provide appropriate rest periods for workers. Consult Industrial Hygiene for appropriate work/rest schedules.
   SOTR also
  • Ensure subcontractor personnel abide by their Jefferson Lab accepted procedure or this procedure's requirements.
  • Inform subcontracted workers of thermal stress warnings and notifications.
  • Ensure subcontracted workers are properly advised of work modification and rest periods.
  • Ensure fluid replacement sources and shelter techniques are available.
  • Notify ESH&Q of thermal stress areas that may require monitoring.
  • Review and accept subcontractor's heat and cold (thermal) stress program which must meet or exceed the requirements of this Jefferson Lab program;

Document Control:
    TECHNICAL POINT-OF-CONTACT:  Jennifer Williams
    APPROVAL DATE:   05/29/19
    REVIEW DATE:  05/29/22
    • Revision 2.0 - 05/29/19  'Heat and Cold Stress Mitigation Program' retitled 'Thermal Stress' to reflect current lab operations; clarified responsibilities
    • Revision 1.4 - 06/19/18  Updated TPOC to J.Williams.
    • Revision 1.3 - 06/04/15  Periodic Review; updated Industrial Hygiene responsibilities.
    • Revision 1.2 - 09/27/12  Periodic review. No changes required.
    • Revision 1.1 - 05/10/11  Updated to provide for "hot work" activities
    • Revision 1.0 - 05/09/09  Updated to reflect current laboratory operations.


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