1.2 Why one worker goes down and another does not

1 The published risk factor list

The OSHA-NIOSH InfoSheet lists the factors that increase a worker's risk. It is worth reading as a checklist rather than as prose, because every line is a question a foreman can actually ask.

Notice how many of the thirteen have nothing to do with the weather. A jobsite that only watches the forecast is monitoring one line of a thirteen-line list.

2 Personal factors nobody sees from across the site

Three of those lines are private, and none of them shows up in a tailgate meeting unless the crew has a reason to speak.

Medications. The InfoSheet names blood pressure medication and antihistamines as examples. A worker taking either is not doing anything wrong, and neither is a medical question for a foreman — but the person taking them should know that their body's response to heat may be different, and that is a training point, not a screening tool.

Prior heat illness. The InfoSheet lists previous heat-related illness as a risk factor for another one. Someone who went down last August is not "over it" this August.

Health conditions and conditioning. Poor physical condition or health problems are on the list. Cold has its own version: OSHA's Cold Stress Guide names hypertension, hypothyroidism and diabetes, plus poor physical conditioning, wetness, dressing improperly and exhaustion.

3 The one factor that outweighs the rest

Lack of recent exposure — being unacclimatized — is the factor with the body count attached to it. OSHA states that over 70 percent of heat-related deaths occur during a worker's first week of work. Not the hottest week. The first one.

The case that shows it best is Summary Nr 149868.015 from May 16, 2022. A helper installing interior walls and ceilings at a commercial site was on his first day of work. There was no shade available other than inside the employees' vehicles. He reported that he was not feeling well and had stopped sweating. He died of heat stroke after finishing the shift. The heat index that day ranged from 71 to 96 °F — nothing that would have made the news — and OSHA's abstract states plainly that he was not acclimated to the heat he was exposed to and had not been trained to identify heat illness symptoms.

Two details in that record deserve to be read twice. He had been drinking: a sports drink at the first break, another at lunch, water later. Water and sports drinks were provided on site. Hydration did not save an unacclimatized body in a full-sun job with no shade. And "stopped sweating" is in the abstract — the crew heard the single most alarming symptom a heat casualty can report, without knowing what it meant.

4 How the day itself shifts the risk

Even with the same people, risk moves during a shift and across a season.

1. 1
   The first hot spell of the year is the dangerous one. A crew that has been working in 70 °F weather is unacclimatized to 95 °F, whatever their years of experience. OSHA advises being extra vigilant during heat waves, when temperatures rise above normal.
2. 2
   Heat load accumulates across a shift, so the afternoon is not the morning. In the fatal cases cited in this course, collapse times cluster in the afternoon: 3:00, 3:15, 3:30, 4:00, 5:24 p.m.
3. 3
   Consecutive days matter. A body that did not fully recover overnight starts the next day behind, especially if sleep was poor in an un-air-conditioned home.
4. 4
   A change in the job changes the exposure. Moving from an air-conditioned plant to an outdoor yard, or from equipment to hand digging, is a new heat exposure even for a long-time employee.

5 Who is on the crew today?

The useful output of this chapter is a two-minute exercise the foreman runs at the tailgate, out loud, before the work starts.

Those four questions find most of the risk on most crews, and each one has an action attached: the new person gets the acclimatization schedule from the next chapter, the returning person gets the shorter one, the heaviest job gets rotated or re-scheduled, and the worker in sealed PPE gets shorter cycles and closer watching. None of it requires a meter.

6 Risk factors in cold work

Cold has a shorter published list, and it is worth memorizing because it explains almost every cold injury story. OSHA's Cold Stress Guide names wetness and dampness, dressing improperly, and exhaustion; predisposing health conditions such as hypertension, hypothyroidism and diabetes; and poor physical conditioning.

Wetness leads the list for a reason. Rain, snow melt, sweat under insulation, a boot that took on water at 9 a.m. — all of them convert a manageable day into a cold injury. Exhaustion is the other one crews underrate: a tired worker generates less heat, makes worse decisions about breaks, and is often the last one still outside finishing up.