Thermal & Hot Operations Safety

This document will go over Hot environments and Illness prevention basic information.
Part 1: Heat Stress Safety
Heat Stress Causes & Symptoms
When can heat stress occur?
  • Primary Trigger: Prolonged exposure to temperatures above 80°F combined with continuous physical movement or work.
  • Aggravating Factors: High exertion, high humidity, low airflow, radiant heat sources, dehydration, alcohol or caffeine use, certain medications, and non-breathable clothing or heavy PPE.
Remember: Air temperature is only one factor. Work intensity, humidity, clothing, PPE, and hydration can significantly increase heat stress risk.
What are the symptoms of heat illness?
Heat Exhaustion
  • Pale skin
  • Muscle cramps
  • Headache
  • Dizziness
  • Weakness or fatigue
  • Hyperventilation
  • Elevated heart rate
  • Body temperature between 101°F and 104°F
  • Nausea or vomiting
Heat Stroke — Medical Emergency
  • Red or dry skin
  • Excessive sweating or inability to sweat
  • Body temperature above 104°F
  • Confusion
  • Slurred speech
  • Aggression or agitation
  • Hallucinations
  • Seizures
  • Fainting
Call 911 immediately if heat stroke is suspected.
Immediate Response: Move the person to a shaded or cooler area, begin cooling measures, and provide water when appropriate.
Worksite Temperature Protocols & Hydration
80°F and Higher
  • Use a buddy system or check in frequently with a supervisor.
  • Monitor yourself and coworkers for signs of heat illness.
  • Maintain access to clean drinking water.
  • Take preventative cool-down breaks when overheated.
  • Report symptoms immediately.
90°F and Higher
  • Participate in pre-shift safety briefings on heat illness prevention.
  • Maintain hydration and buddy-system monitoring.
  • Take a mandatory 10-minute cool-down break every two hours.
100°F and Higher
  • Continue all high-heat precautions.
  • Increase monitoring for heat illness symptoms.
  • Take a mandatory 10-minute cool-down break at least every hour.
Preventative Breaks Matter: Employees should not wait until symptoms develop before taking a cool-down break.
Hydration & Cool-Down Guidance
  • Hydration: Drink water regularly throughout the shift rather than waiting until you feel thirsty.
  • Water Access: Employees must have access to clean drinking water during the shift.
  • Cool-Down Areas: Use open-air shade or air-conditioned spaces for recovery breaks.
  • Symptom Reporting: Any heat-illness symptom should be reported to a supervisor immediately.
Acclimatization & Supervision

Acclimatization is the process of gradually adapting the body to work in hot environments over approximately 7 to 14 days.

New Workers

Limit initial heat exposure to a maximum of 20% of a full shift on Day 1, increasing exposure by no more than 20% on each subsequent day.

Experienced Workers
  • Day 1: Up to 50% exposure
  • Day 2: Up to 60%
  • Day 3: Up to 80%
  • Day 4: Up to 100%
Medical Adjustments: The acclimatization period should be extended when relevant medical conditions or other risk factors require additional adjustment.
Supervision Requirements
  • New employees must be closely observed by a buddy or supervisor during their first 14 days of employment.
  • Previously exposed employees must be observed using the buddy system whenever temperatures exceed 80°F.
  • Supervisors should monitor workers for changes in behavior, coordination, speech, or physical condition.
Do Not Leave a Symptomatic Worker Alone: Heat illness can progress quickly. Maintain observation and escalate medical response when needed.
Part 2: Hot Work Safety
What is Hot Work?

Hot work is any operation involving open flames or producing heat and/or sparks capable of initiating fires or explosions.

This includes welding, brazing, cutting, soldering, grinding, torching, and similar spark- or heat-producing tasks. Hot work requires strict site controls and may require a designated permit and fire watch.

Need a Hot Work Permit?

Request permits through your scheduler or submit the online request form.

Hot Work Permit Request Form
Hot Work Activities & Ignitable Materials
Common Hot Work Activities
  • Welding, including pin and orbital welding
  • Brazing & soldering
  • Carbon-arc gouging
  • Torching & torch-applied roofing
  • Smelting & heat treating
  • Hot riveting
  • Grinding, chipping, & abrasive blasting
  • Cutting, including chop saws and plasma cutters
Remember: Unlisted activities producing sparks, heat, or flame must also be assessed for ignition potential before work begins.
Examples of Common Ignitable Materials
  • Wood, paper, and cardboard
  • Insulation & building finishes
  • Flammable chemicals & solvents
  • Combustible dusts & hazardous gases
Permit Requirements & Location Restrictions
What is a Hot Work Permit?

A Hot Work Permit is an authorized document posted at the job site containing critical safety details, including:

  • Date and time of work
  • Specific location
  • Scope of hot work
  • Assigned safety team members
  • Required fire prevention controls
Sample Hot Work Permit Tag
When is a Permit Required?
A Hot Work Permit is required whenever hot work is performed outside of a pre-approved Designated Hot Work Area.
Where is Hot Work Strictly Prohibited?

Hot work cannot proceed in locations with any of the following conditions:

  1. Areas not authorized by Management, the PAI, or EHS Fire & Life Safety.
  2. Areas with explosive atmospheres or combustible dust levels capable of posing a flash fire hazard.
  3. Areas with uncleaned equipment, tanks, drums, or containers that may produce explosive or toxic vapors when heated.
  4. Areas where fire protection systems are impaired without approved alternative safety precautions.
Prohibited Practice: Taping over, placing plastic bags, or putting unapproved coverings over smoke detectors is never an acceptable impairment mitigation method at UW–Madison.
Designated Hot Work Areas

A Designated Area is a permanent, dedicated space optimized for hot work, such as a shop.

Before work begins, the area must meet all of the following criteria:

  1. Constructed of fire-resistant materials.
  2. Posted with required warning signage specified by the PAI.
  3. Inspected at least annually by the PAI.
  4. Equipped with inspected and accessible fire extinguishers.
  5. Maintained with properly functioning machinery and tools.
  6. Provided with adequate and operational local exhaust ventilation.
If any of these conditions are missing or compromised, the area loses its designated status and a Hot Work Permit is required until the issue is corrected.
Hot Work Safety Team Roles (NFPA 51B)

A hot work safety team includes three distinct roles. All roles are empowered and required to stop work immediately when conditions become unsafe.

Permit Authorizing Individual (PAI)

Inspects the work site, identifies hazards, verifies combustible separation, determines required PPE, issues permits, and enforces shutdowns or extended fire watches when hazards arise.

Hot Work Operator

Performs the hot work activity, obtains PAI approval, inspects tools and site conditions, follows permit requirements, and stops work when conditions become hazardous.

Fire Watch

Monitors for ignition risks and sparks, is trained to activate the fire alarm and use an extinguisher, and is authorized to stop unsafe work.

Both the Operator and Fire Watch must read, understand, follow, and sign the Hot Work Permit.
Fire Watch Requirements & Duration
When is a Fire Watch Required?
  • When required by the PAI or EHS Fire & Life Safety.
  • When hot work is performed outside a designated area and within 35 feet of easily ignitable materials or openings.
  • When combustible materials are located on the opposite side of metal walls, partitions, or ceilings being worked on.
  • When operator PPE could ignite, retain sparks, or create additional hazards.
  • When conditions could allow anything greater than a minor, well-contained fire to develop.
Duration & Duties
  • Standard Duration: The fire watch remains posted for at least 1 hour after hot work has stopped.
  • Extensions: The PAI or EHS Fire & Life Safety may extend the duration.
  • Secondary Tasks: Light secondary duties may be performed only if they do not interfere with continuous observation of the hot work area.
Part 3: Contacts & Standards
Regulatory Standards & Contact Information
Applicable Regulatory Standards
  • NFPA 51B (2019 Edition): Standard for Fire Prevention During Welding, Cutting, and Other Hot Work.
  • OSHA 29 CFR 1910 Subpart Q: Welding, Cutting, and Brazing — General Industry.
  • OSHA 29 CFR 1926 Subpart J: Welding and Cutting — Construction Industry.
Contact & Assistance

For support regarding heat illness prevention, hot work permits, site evaluations, or policy compliance, reach out to the appropriate team below:

EHS Front Office: (608) 265-5000 EOH Phone: (608) 890-1992 Email EOH Email Fire & Life Safety
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Keywords:
hot work, hot, work, fire, Fire and Life, Safety, EHS, Environmental Health and Safety, Workplace Safety, hot work permit, Heat, Hot, heat exhaustion, summer, sunny, warm, EHS, workplace safety, stress, heat stress 
Doc ID:
164143
Owned by:
Sophie J. in Facilities KB DEMO
Created:
2026-09-14
Updated:
2026-09-14
Sites:
Facilities KB DEMO