Sheet 16Domain 3 of 5 · Health Hazards and Basic Industrial Hygiene
Heat and cold stress: signs, controls and STSC practice
No federal standard sets heat or cold limits for construction work as of October 2026. OSHA handles heat stress on construction sites through the General Duty Clause and a heat National Emphasis Program, and the practical rules come from OSHA and NIOSH guidance. This sheet sorts out which guidance stands behind which answer, and the cards put it to work on roofs, decks and trenches in both seasons.
Where the rule behind each heat or cold answer comes fromscroll →
Topic
Source of the rule
Where it trips people up
Heat illness prevention
General Duty Clause, Section 5(a)(1) of the OSH Act, plus OSHA's National Emphasis Program on heat
Hunting for a numeric limit when the duty is a general one
A federal heat standard
Proposed by OSHA in 2024; not a final rule as of October 2026
Treating the proposal's trigger temperatures as law
Water, rest and shade
OSHA heat guidance
Reading guidance amounts as legal minimums
Acclimatization
NIOSH recommendations
Assuming a fit, experienced worker needs no ramp-up
Cold stress
OSHA and NIOSH cold-stress guidance; no construction standard of its own
Treating every cold injury the same way
OSHA's heat rulemaking page tracks the proposal. If you test well after October 2026, check it for a change in status.
Talking point 02
Heat and cold cards
Summer roofs and closed-up floors, winter pours and wet trenches: the scenes run across both seasons, from the first sign of trouble to a medical emergency.
Card 1 of 15 · 0 right
Card 1
A drywall hanger on an unventilated upper floor in August reports headache, nausea and dizziness and is sweating heavily, but is alert and answering questions clearly. What should the supervisor do?
Pick an answer. A short note for each option, A to D, appears here.
ASalt tablets are no longer recommended and can upset the stomach, and 15 minutes is too short to judge recovery from heat exhaustion.
BCorrect: These are heat exhaustion signs; cooling, fluids and close observation are the first aid, and worsening symptoms mean calling 911.
CContinuing in the same heat lets heat exhaustion progress, possibly to heat stroke; the worker needs to stop and cool down.
DA worker with heat exhaustion should not be left alone or allowed to drive, because symptoms can worsen quickly into heat stroke.
Card 2
During a winter pour, a finisher who has been wet for hours is shivering violently, fumbling tools and slurring words. What should the supervisor do FIRST?
Pick an answer. A short note for each option, A to D, appears here.
AActivity alone cannot rewarm a wet worker who is confused and slurring words; those signs point to hypothermia that needs shelter and care.
BCorrect: Slurred speech and fumbling signal hypothermia, so the worker needs removal from the cold and wet, gentle rewarming, and medical help.
CCaffeine is a poor choice, and sending the worker back to the pour after a short break ignores signs that need medical evaluation.
DRubbing cold extremities can damage tissue and send cold blood toward the core; rewarming should start at the trunk.
Card 3
Pipe layers stood in water in a trench for several days in 40°F weather. Their feet are now red, swollen, tingling and numb, with no frozen tissue. Which condition is MOST likely?
Pick an answer. A short note for each option, A to D, appears here.
AChilblains are small itchy red patches from repeated cold exposure, not swelling and numbness after days of wet feet.
BFrostbite requires frozen tissue, and the scenario states that no tissue is frozen.
CHypothermia is a drop in core body temperature with shivering and confusion, not a local injury to the feet.
DCorrect: Trench foot is a non-freezing injury from prolonged wet, cold feet, marked by redness, swelling, tingling and numbness.
Card 4
A new laborer joins a roofing crew during a heat wave. Under NIOSH acclimatization guidance, how much of a full shift's heat exposure should this worker have on day 1?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: NIOSH advises that new workers start at no more than 20% of the usual exposure on day 1, adding no more than 20% each day.
BEighty percent is a late step in the schedule for workers who already have heat experience, not a day-1 limit for a new worker.
CFifty percent is the day-1 starting point for workers with previous heat experience, not for a newly hired laborer.
DWater replaces sweat losses but does not acclimatize the body, and most heat deaths happen in the first few days on the job.
Card 5
A laborer is found confused and stumbling on a hot slab while still sweating heavily. The supervisor has called 911. What should be done NEXT while waiting for EMS?
Pick an answer. A short note for each option, A to D, appears here.
AWalking a confused, unsteady worker risks a fall and delays cooling, which should begin right where the worker is.
BHeat stroke victims may still sweat, especially after exertion; confusion is the deciding sign, and waiting delays treatment.
CCorrect: Confusion means heat stroke, and rapid cooling with cold water or ice while EMS is on the way is what improves survival.
DA confused worker may choke, and drinking cannot lower body temperature fast enough to treat heat stroke.
Card 6
Which of the following is a sign that a construction worker may be experiencing frostbite?
Pick an answer. A short note for each option, A to D, appears here.
AA flushed face and fast breathing fit heat strain or exertion, not frozen tissue.
BA raised heart rate and blood pressure are general stress responses and do not identify frostbite.
CCorrect: Frozen tissue looks white or grayish-yellow and feels waxy or hard, the classic signs of frostbite.
DHeavy sweating and thirst are signs of heat stress, the opposite of a cold injury.
Card 7
At the end of a hot week, a laborer reports muscle pain, unusual weakness and dark, cola-colored urine. What should the supervisor suspect?
Pick an answer. A short note for each option, A to D, appears here.
ADark urine can come from dehydration, but together with muscle pain and weakness it suggests muscle breakdown that needs a medical exam.
BHeat cramps cause painful spasms but not cola-colored urine, which signals muscle protein passing into the urine.
COrdinary soreness does not darken the urine, and treating this as routine can delay care for possible kidney damage.
DCorrect: Muscle pain, weakness and cola-colored urine point to rhabdomyolysis, which can damage the kidneys and needs prompt medical care.
Card 8
Why does OSHA heat guidance recommend a buddy system for crews working in hot conditions?
Pick an answer. A short note for each option, A to D, appears here.
APairing workers is about watching each other for symptoms, not about dividing the physical workload.
BThere is no final federal heat standard; OSHA addresses heat through guidance and the General Duty Clause.
CEach worker needs ready access to plenty of cool water, and sharing one supply is not the purpose of a buddy system.
DCorrect: Heat illness can cloud a worker's judgment, so a partner is more likely to notice early symptoms and get help.
Card 9
Which returning or current worker should the supervisor treat as UNACCLIMATIZED and put on a gradual heat-exposure schedule?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: Acclimatization fades after about a week away from heat, so a two-week absence calls for a gradual return schedule.
BA worker moving from another hot crew keeps the adaptation already built and does not need to restart.
CWorking in the heat every day for a month is exactly how a worker becomes and stays acclimatized.
DA single day off is too short to lose heat acclimatization.
Card 10
An asbestos-abatement crew wears impermeable disposable coveralls and respirators in an un-air-conditioned building on an 88°F day. What should the supervisor recognize about their heat risk?
Pick an answer. A short note for each option, A to D, appears here.
AThe heat index assumes light clothing and shade; it does not reflect impermeable suits and respirators, which add heat load.
BGetting out of the sun helps, but an unventilated building plus protective clothing can still create high heat strain.
CCorrect: Impermeable coveralls stop sweat from evaporating, the body's main way to cool, so heat strain can build at moderate temperatures.
DNo single 90°F threshold exists; clothing, workload and acclimatization can make 88°F dangerous.
Card 11
Which sign MOST clearly indicates that a worker's heat illness has progressed to heat stroke?
Pick an answer. A short note for each option, A to D, appears here.
ADizziness that clears with rest is typical of heat exhaustion or fainting, not heat stroke.
BPainful cramps are heat cramps from salt and fluid loss, an early and milder stage of heat illness.
CHeavy sweating and thirst occur with heat exhaustion and do not by themselves show that the brain is affected.
DCorrect: Altered mental status such as confusion or slurred speech is the defining sign of heat stroke, a medical emergency.
Card 12
Which heat-stress control for an outdoor crew is an ENGINEERING control?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: Engineering controls change the work environment itself, and shade or spot cooling lowers the heat load on the whole crew.
BMoving heavy tasks to cooler hours changes how work is organized, which makes it an administrative control.
CCooling vests are worn by each worker, so they count as personal protective equipment.
DAn acclimatization schedule is a work-practice policy, which places it among administrative controls.
Card 13
According to OSHA's heat illness prevention guidance, how much water should workers doing moderate work in the heat drink?
Pick an answer. A short note for each option, A to D, appears here.
AA large volume every two hours cannot keep pace with steady sweat losses; smaller, frequent drinks work better.
BThirst lags behind fluid loss, so waiting for it lets dehydration build during the shift.
CCorrect: OSHA's water-rest-shade guidance calls for about 1 cup every 15 to 20 minutes during moderate work, even without thirst.
DEnergy drinks with caffeine and sugar are not recommended as a replacement for water during hot work.
Card 14
Which measurement BEST reflects the combined heat stress from air temperature, humidity, radiant heat from the sun, and air movement?
Pick an answer. A short note for each option, A to D, appears here.
ADry-bulb temperature measures only the air and ignores humidity, sun and wind.
BRelative humidity shows moisture in the air but not temperature, radiant heat or air movement.
CThe heat index combines temperature and humidity for shaded conditions, so it leaves out direct sun and wind.
DCorrect: WBGT combines air temperature, humidity, radiant heat and air movement, which makes it the preferred heat-stress index.
Card 15
Before winter bridge work begins, a supervisor trains the crew on cold stress. Below what core body temperature is a worker considered to have hypothermia?
Pick an answer. A short note for each option, A to D, appears here.
A98.6°F is about normal core temperature. Hypothermia starts well below that.
BA dip to 97°F is a small drop, not yet hypothermia, though a cold worker still needs warming.
CCorrect: Hypothermia means a core body temperature below 95°F, when the body loses heat faster than it can produce it.
DWaiting for 90°F misses the warning stage. By then hypothermia is serious and shivering may already have stopped.
Talking point 03
What the scene adds to the thermometer
The forecast high is only part of the heat load. A sunlit roof, a fresh asphalt mat, the cab of an old loader with no air conditioning, a heavy task scheduled for mid-afternoon: each raises it without changing the number on your weather app. Cold works the same way through wind and wet clothing.
Talking point 04
Heat and cold terms worth knowing
Heat rash
Clusters of small, itchy red bumps where sweat stays on the skin, often under a harness or at the collar. A sign the crew is sweating hard.
Heat cramps
Painful muscle spasms during or after heavy sweating, when the body has lost salt along with water.
Heat syncope
Fainting or light-headedness, typically after standing still a long time or getting up fast in the heat.
Wind chill
How cold exposed skin feels once wind is added. A breezy 35°F bridge deck can be harder on a crew than a still day several degrees colder.
General Duty Clause
Section 5(a)(1) of the OSH Act: employers must keep the workplace free of recognized hazards likely to cause death or serious harm. OSHA uses it for heat cases because no heat standard exists.
National Emphasis Program
An OSHA enforcement plan that points inspections at one hazard. The heat program sends inspectors to high-heat industries on hot days.
Talking point 05
A heat and cold plan for one site
Someone checks the forecast each morning and adjusts the day's schedule
Cool drinking water within a short walk of every crew, refilled during the shift
A shaded or cooled rest area set up before the hot season starts
A written ramp-up schedule for workers new to the heat, following NIOSH acclimatization guidance
Heavy tasks moved to cooler hours on high-heat days
Warm, dry break space and spare dry gloves and socks on cold jobs
Every worker trained to spot heat and cold illness, with the site address ready for a 911 call