Heat Illness Prevention - Cal/OSHA

Heat illness has a cruel design flaw: it dulls the judgment you would need to notice it. A worker getting into trouble tends to be the last one to say so, because confusion, irritability, and "I'm fine" are symptoms too. This Cal/OSHA Heat Illness Prevention Toolbox Talk covers the rule California wrote around that flaw: Title 8, Section 3395, the Maria Isabel Vasquez Jimenez heat illness standard. It applies to all outdoor places of employment, and it names construction as one of the industries that must follow its high-heat procedures. Federal OSHA has proposed a heat rule, but it is not final. In California, this one is already the law.

Where the boundary of this talk sits#

This talk covers what Section 3395 requires on an outdoor California job. The body's response and first aid belong to the heat stress talk, drinking habits to the hydration talk, and sunburn to the sun protection talk. Indoor heat is a separate California rule.

The anchor#

Here is the distinction that carries this whole talk: California's heat rule moves the decision out of the worker's head and onto the thermometer and the supervisor's eyes — water from the first hour, shade once it passes 80°F, a full set of high-heat procedures at 95°F, and close watching of anyone new or anyone working through a heat wave — because the person who most needs to stop is the person least able to judge it, and "I feel fine" is not a reading.

Water: from the first hour, not the first complaint#

Section 3395(c) requires potable drinking water that is fresh, pure, suitably cool, and free of charge, located as close as practicable to where people are working. Where water is not plumbed in, there must be enough at the start of the shift for one quart per employee per hour for the entire shift. A crew can start with less only if the employer has an effective way to refill it during the shift so everyone can still drink a quart or more an hour.

Do the math out loud at the tailgate. Ten workers on a ten-hour shift is 100 quarts, or 25 gallons. One cooler on the tailgate of a pickup is not that. The rule also requires training on drinking small amounts often — up to four cups per hour when it is hot and people are sweating more than usual (Section 3395(h)(1)(C)).

Shade: at 80°F it must already be up#

Under Section 3395(d)(1), when the temperature exceeds 80°F, shade must be present at all times while employees are there, as close as practicable to the work. The temperature means the dry-bulb reading taken in an unshaded spot. There must be enough shade for everyone on a rest or recovery break to sit in a normal posture fully in the shade without touching each other, and enough for everyone who stays on site for the meal period. Below 80°F, shade is either up or provided promptly when a worker asks.

Shade that is itself too hot does not count — the rule says shade is not adequate when heat in the shaded area defeats its purpose, so a car sitting in the sun is not shade unless it is running with the air conditioning on. And outside agriculture, an employer can use cooling measures such as misting machines instead of shade only if it can show they are at least as effective as shade.

The cool-down rest: the worker asks, the rule protects#

Section 3395(d)(3) says employees must be allowed and encouraged to take a preventative cool-down rest in the shade whenever they feel the need. A worker who takes one must be monitored and asked whether they have heat illness symptoms, encouraged to stay in the shade, and not ordered back to work until symptoms are gone — and never in less than 5 minutes, not counting the time it took to get to the shade.

A cool-down rest is not a break to be counted against anyone. It is the moment a supervisor gets to look closely at someone who may be starting to fail.

High-heat procedures at 95°F#

When the temperature reaches 95°F or more, construction is one of the named industries that must switch to high-heat procedures under Section 3395(e). The crew must be able to reach a supervisor by voice, observation, or electronic means. Employees must be observed for alertness and signs of heat illness by one of four methods: a supervisor or designee watching 20 or fewer employees, a mandatory buddy system, regular radio or phone contact with a worker who is alone, or another effective means. One or more employees on each site must be designated as authorized to call emergency medical services. Workers must be reminded throughout the shift to drink plenty of water. And pre-shift meetings must review the high-heat procedures before work starts, encourage everyone to drink plenty of water, and remind them of their right to take a cool-down rest.

New workers and heat waves#

Acclimatization — the body adapting to heat — builds gradually and peaks in most people within four to fourteen days. That is why Section 3395(g) requires close observation by a supervisor or designee of every employee during a heat wave, and of any employee newly assigned to a high-heat area for their first 14 days. Section 3395(g)(1) defines a heat wave as a day when the predicted high is at least 80°F and at least ten degrees higher than the average high of the previous five days. The new hire and the first hot day after a mild week are where heat illness hides.

When someone goes down#

Section 3395(f) requires written emergency procedures: effective communication, responding to signs and symptoms with first aid or emergency services, contacting emergency medical services, and making sure clear and precise directions to the site can and will be given. Under (f)(2)(C), an employee showing signs or symptoms of heat illness must be monitored and must not be left alone or sent home without being offered onsite first aid or provided with emergency medical services. Sending a confused worker to drive home is the scenario this line was written to stop.

Where the duty sits#

8 CCR 3395 carries the whole duty: (c) water, (d) shade and cool-down rests, (e) high-heat procedures at 95°F, (f) emergency response, (g) acclimatization, (h) training for employees and supervisors before they work in the heat, and (i) a written Heat Illness Prevention Plan in English and in the language understood by the majority of employees, available at the worksite. This meeting also counts toward 8 CCR 1509(e), which requires toolbox or tailgate safety meetings at least every 10 working days.

What can go wrong?#

• One water cooler for a ten-person crew on a 98°F day, with no plan to refill it.
• Shade goes up at noon instead of when the thermometer passed 80°F at 10 a.m.
• A worker who asks for a cool-down rest is told to "push through till lunch."
• A worker who is dizzy and confused is sent home in his own truck.

How do we manage this properly?#

• Measure, don't guess — check the temperature in an unshaded spot and log when it passes 80°F and 95°F.
• Water for the whole shift — one quart per person per hour, close to the work, cool, with a refill plan.
• Shade before 80°F — enough for everyone on break to sit fully in it without touching.
• Protect the cool-down rest — at least 5 minutes, monitored, and nobody sent back with symptoms.
• Switch modes at 95°F — pre-shift meeting, named observers or buddies, a designated person to call 911.
• Watch the new and the heat wave — first 14 days, and every worker when the heat jumps.

Before you start#

Read today's forecast and decide now who checks the thermometer and when. Count the water against the crew and the shift length. Confirm the shade location and that it will fit everyone on break. If 95°F is possible, name the buddies or observers and the person authorized to call emergency services, and make sure everyone can give clear directions to the site. Point out anyone in their first 14 days.

Talk it over#

• What would you notice first if the person next to you was getting heat illness?
• Where is today's shade, and does it fit all of us sitting down?
• Who is authorized to call 911 today, and what address would they give?

The bottom line#

In California, heat protection runs on the thermometer and the supervisor's eyes, not on how anyone feels. Water from the first hour, shade over 80°F, a protected cool-down rest of at least 5 minutes, high-heat procedures at 95°F, and close watching of new workers and everyone during a heat wave. A worker with symptoms is never left alone and never sent home without first aid being offered.

Frequently asked questions about Cal/OSHA heat illness prevention#

Does Section 3395 apply to construction?

Yes. It applies to all outdoor places of employment, and subsection (a)(2) names construction among the industries that must also follow the high-heat procedures in subsection (e) at 95°F and above.

Is there a federal OSHA heat standard?

Not a final one. OSHA published a proposed rule on August 30, 2024, and the public hearing closed in 2025, but no final rule is in effect. In California, Section 3395 already applies.

Download the Cal/OSHA heat illness prevention toolbox talk PDF#

Download this Cal/OSHA Heat Illness Prevention Toolbox Talk as a printable PDF in English and Spanish, and read it at the water cooler before the thermometer passes 80°F.

Related toolbox talks#

• Heat Stress
• Hydration
• Sun Protection and UV Exposure
• First Aid and AED

Sources#

• Cal/OSHA, Title 8 CCR §3395 — Heat Illness Prevention in Outdoor Places of Employment ((a) scope and industries for high-heat procedures; (b) definitions of acclimatization, shade, temperature; (c) one quart per employee per hour; (d) shade over 80°F and cool-down rest of at least 5 minutes; (e) high-heat procedures at 95°F; (f) emergency response; (g) acclimatization, heat wave definition in (g)(1), and 14-day observation; (h) training; (i) written plan): https://www.dir.ca.gov/title8/3395.html
• Cal/OSHA, Title 8 CCR §1509 — Injury and Illness Prevention Program ((e) toolbox or tailgate meetings at least every 10 working days): https://www.dir.ca.gov/title8/1509.html
• OSHA, Heat Injury and Illness Prevention in Outdoor and Indoor Work Settings Rulemaking (proposed rule Aug. 30, 2024; no final rule in effect): https://www.osha.gov/heat-exposure/rulemaking

Written by FieldSafetyTalk's safety professional — a CSP, ASP, CHST and OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.

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