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Heat Safety in Greenhouses

A greenhouse traps sun and humidity by design, so working inside can be hotter than working in the field. The plan should assume that, not discover it midday.

Why are greenhouses so hot?

Glass and plastic coverings let sunlight in and keep heat from escaping. Humidity from watering and plants makes it harder for sweat to evaporate, so the body cools less effectively.

The conditions that help plants thrive are often tough for people. A mild day outside may be a heavy-strain day inside.

Plan for humidity as well as temperature. When the air is saturated, sweat does not evaporate, so the body may feel fine until it suddenly does not.

• Trapped heat and humidity
• Sweat evaporates less in humid air
• Glass and plastic hold solar heat
• Humidity from watering and plants

Which tasks add to the load?

Potting, moving trays, harvesting, watering and cleaning involve steady movement in warm, damp air. Work near heaters, in the upper levels of a structure or in closed corners may be hotter still.

Protective equipment for applying chemicals can trap more heat. Follow the label and manufacturer instructions, and check with EPA or your extension office for guidance.

Keep walkways clear and lighting adequate so a person who feels faint can leave quickly, and so a coworker can find them. Mark exits clearly.

• Heavy lifting of trays and pots
• Spraying in protective clothing
• Work in closed or upper areas
• Long shifts without a break outside
• Check labels for re-entry instructions
• Ask EPA or extension about protective gear

How can the space be made more comfortable?

Ventilation, shade cloth, fans and cooling systems can lower temperatures where the structure allows. Ask a greenhouse specialist or extension agent what suits your design.

Keep systems maintained. A vent or fan that fails on a hot afternoon creates a dangerous space, so test them before the season.

Heat can combine with fertilizer or chemical applications, so read product labels and follow re-entry instructions from the manufacturer and EPA guidance.

• Test vents and fans before the season
• Keep cooling systems maintained
• Shade cloth where the structure allows
• Fans sized by a specialist

How should breaks be organized?

Put the rest area outside the greenhouse, in a cooler, shaded place with water. A break inside the same hot air does little for recovery.

Rotate people through the hottest tasks and use shorter shifts inside. For schedules and limits, use NIOSH and OSHA guidance instead of remembered numbers.

Train every worker, including family helpers, on the signs of heat illness and on where to go and whom to call. Repeat the briefing at the start of each hot spell.

• Take breaks outside the greenhouse
• Rotate people through the hottest tasks

What signs should crews watch for?

Heavy sweating, dizziness, headache, nausea, cramps, unusual fatigue and irritability are common early signs. Plants are everywhere and can hide a person who has gone down.

Confusion, fainting or a seizure means call 911 right away. Avoid working alone in a large greenhouse, or arrange regular check-ins.

Keep a record of what works, such as which vents, fans or schedules kept the space tolerable, so you can repeat it next season.

• Keep exits and walkways clear
• Check in on anyone working alone

What about seasonal and young workers?

Greenhouse and nursery operations often hire seasonal and young workers. Provide a clear orientation on heat, water, breaks and who to tell.

Check youth work rules with the U.S. Department of Labor and your state agency, and confirm there.

Ask your insurer or extension office about safety resources, and use their checklists to review your greenhouse for heat risks before summer.

• Orientation on heat, water and breaks
• Youth rules confirmed with the Department of Labor

Where can you get official help?

NIOSH, OSHA and land-grant extension offices publish heat and greenhouse guidance. Requirements for employers vary by state and operation size, so confirm what applies to you.

An occupational health provider can advise on medical concerns, such as the effect of certain conditions or medicines on heat tolerance.

• Ask NIOSH and OSHA for current guidance
• Ask a clinician about conditions and medicines

Last reviewed: November 12, 2026. Written by the Farm Safety Editorial Team. See our editorial policy.