2.3 Water, rest and shade, in numbers

1 How much water, and how often

The OSHA-NIOSH InfoSheet gives the working figure: during moderate activity in moderately hot conditions, workers should drink about 1 cup every 15 to 20 minutes. OSHA's Heat Stress Guide says the same thing from the other side — thirst cannot be relied on as a guide to the need for water; instead, water must be taken every 15 to 20 minutes in hot environments.

Turn that into volume. Four 8-ounce cups an hour is 32 fluid ounces — exactly one quart per hour, which is also the supply figure in OSHA's proposed rule. Three cups an hour is 24 ounces. Over an 8-hour shift in the heat, that is 1.5 to 2 gallons per worker; for a crew of six, 9 to 12 gallons on the truck before anything gets spilled. The water intake calculator does the arithmetic for any crew size and shift length.

2 How much is too much

Water has an upper limit, and this is the part most heat training skips. The OSHA-NIOSH InfoSheet states that workers should be made aware that it is harmful to drink extreme amounts of water and should generally not drink more than 12 quarts (48 cups) in a 24-hour period. NIOSH guidance adds an hourly ceiling: fluid intake should generally not exceed 6 cups per hour.

Past those amounts, drinking dilutes the body's sodium instead of correcting dehydration. The InfoSheet also gives the right response to a job that seems to need more: if higher amounts of fluid replacement are needed because of prolonged work in high heat conditions, a more comprehensive heat illness prevention program may be warranted. In other words, if the crew genuinely needs 14 quarts a day, the answer is to change the work, not to add cups.

3 Water people will actually drink

A cooler nobody walks to is not a control. The published details are all about removing reasons to skip a drink.

• Cool. The InfoSheet asks for water at 50-60 °F if possible, with a palatable, odor-free taste.
• Close. Plenty of cool water in convenient, visible locations close to the work area. The proposed rule uses the phrase "readily accessible to the employee."
• Individual cups. A shared dipper is a sanitation problem, and NIOSH's guidance calls for individual drinking cups.
• Enough of it. The proposed rule would require a supply sufficient to provide access to 1 quart of drinking water per employee per hour.

On the electrolyte question the sources are consistent and less dramatic than the sports-drink aisle suggests. The InfoSheet says workers should eat regular meals and snacks, which provide enough salt and electrolytes to replace what is lost through sweating as long as enough water is consumed, and that electrolyte drinks are usually not necessary. NIOSH adds that if sweating lasts for several hours, sports drinks containing balanced electrolytes are appropriate. Both agree that workers should avoid salt tablets, and OSHA's guidance is to avoid alcohol and drinks high in caffeine or sugar.

4 What is already required, and what is proposed

Drinking water on a jobsite is not a heat rule — it is a sanitation rule, and it applies whatever the weather. 29 CFR 1926.51 requires potable water on construction sites; 29 CFR 1910.141 does the same in general industry. Those are current law.

Some State Plans have gone ahead of the federal rulemaking. OSHA's heat standards page lists heat-specific standards in California (Title 8 section 3395, triggered at 80 °F, plus an indoor rule), Colorado (agricultural labor conditions rules), Minnesota (indoor workplaces), Oregon and Washington (outdoor heat exposure), and other states have adopted rules more recently. If you work under a State Plan, its rule is the one that applies to you, and it may be stricter than anything in this table.

5 Rest: the details that decide whether a break is a break

OSHA's proposed rule is unusually specific about rest, and the specifics are there because vague break language gets gamed. At or above the high heat trigger it would require a minimum 15-minute paid rest break at least every two hours, in the break area, with three conditions attached:

1. 1
   A meal break may count as a rest break, even if it is not otherwise required by law to be paid.
2. 2
   Time spent donning and doffing PPE — coveralls, harnesses, respirators — must NOT count toward the rest break.
3. 3
   The time it takes to walk to and from the break area is not included in the break either.

Even below the high heat trigger, the proposal would require employers to allow and encourage employees to take paid rest breaks if needed to prevent overheating. That is the provision that puts a stop in the worker's hands rather than only in the supervisor's.

6 Shade: what counts

Shade is the only control that acts on the radiant pathway, and the proposed rule is precise about what qualifies for an outdoor break area: artificial shade such as a tent or pavilion, or natural shade such as trees, that provides blockage of direct sunlight and is open to the outside air — but not shade from equipment — or air conditioning if the break area is an enclosed space like a trailer, vehicle or structure.

That exclusion matters. The shadow of an excavator or a stack of pallets is not a break area; a hot truck cab with the windows up is not one either, unless the air conditioning is running. In the fatal case discussed in Chapter 1.2, OSHA's abstract records that the worksite was in direct sunlight with no shade available other than within the employees' vehicles.

The break area also has to be sized and placed for use: able to accommodate the number of employees on break, and readily accessible to the work area. Shade three hundred yards away, up a hill, is shade nobody uses at 2 p.m. And air-conditioned break areas do not cost the crew its acclimatization — the InfoSheet states plainly that air conditioning will not result in loss of heat tolerance and is recommended for rest breaks.