In brief
A greenhouse concentrates open-field risks into an enclosed space: temperature and humidity rise together, pesticide vapour does not disperse and combustion products from heaters accumulate. This article explains the management of heat stress, the rules for spraying and re-entry in closed greenhouses, carbon monoxide precautions and the ergonomic strain of harvesting with practical steps.
Why is greenhouse safety different from open fields?
A greenhouse is a climate built for plants, not for people. The temperature and humidity that plants need can mean heat stress for workers. Spray mist that disperses with the wind in an open field hangs in a greenhouse for hours. In winter, the products of the fuel burned to heat the greenhouse also collect in the same enclosed space. Greenhouse safety is therefore achieved not by transferring field measures unchanged but by redesigning them for an enclosed environment.
Agricultural businesses are within the scope of Law No. 6331 on Occupational Health and Safety as long as they employ workers; agriculture is not among the exceptions listed in Art. 2 of the Law. We cover transport, accommodation and hygiene in greenhouses employing seasonal workers in our article on OHS for seasonal agricultural workers. In this article we focus on the inside of the greenhouse.
Working in greenhouse heat: how is heat stress managed?
In summer, the temperature inside a greenhouse can rise well above the outside air. If humidity is also high, sweat cannot evaporate and the body cannot cool itself. For this reason, looking at a thermometer is not enough when assessing work in greenhouse heat; temperature, humidity, solar radiation and the physical demands of the work are considered together.
Annex 1 Art. 19 of the Regulation on Health and Safety Measures in Workplace Buildings and Annexes requires the ambient temperature to be suitable for the working method and the physical effort of the worker, and states that the TS EN 27243 standard can be used to assess thermal comfort. This standard assesses heat stress using the WBGT (wet bulb globe temperature) index, which takes temperature and humidity into account together. We plan the measurement with accredited laboratories; the results are entered into the risk assessment.
Measures that can be applied on site:
- Working hours: Heavy work such as harvesting, carrying and pruning is moved to the early morning and late afternoon; work inside the greenhouse is reduced at midday.
- Shading and ventilation: Shade screens, roof and side vents and fans are operated according to working hours.
- Water and breaks: Cool, easily accessible drinking water and a shaded rest area outside the greenhouse are provided. Breaks are made more frequent as the temperature rises.
- Acclimatisation: For workers who are new or returning from leave, the workload is increased gradually over the first days.
- No lone working: No worker is left alone inside the greenhouse during the hot hours; workers keep an eye on each other.
- Clothing: Light-coloured, breathable clothing and a hat are worn. Because the protective clothing needed to enter after spraying increases the heat load, such work is planned for cooler hours.
For measurement parameters and the assessment approach, see our article on thermal comfort measurement.
Spraying in greenhouses: the rules of an enclosed space
Spraying in a greenhouse can create a higher airborne concentration with less product than in an open area. In methods such as fogging and fumigation, the product is deliberately kept in the air. The rules for spraying in greenhouses are therefore divided into three phases:
- Before spraying: Only trained persons carry out the application. It is checked that no other workers remain in the greenhouse, the entrance doors are closed and a warning sign is posted on the doors showing that spraying has taken place, the date and the re-entry time.
- During spraying: The applicator uses the protective equipment specified on the product label and safety data sheet. The respirator filter must be suitable for the product; a dust mask does not protect against vapour and mist.
- After spraying: Nobody enters without protective equipment until the re-entry interval on the product label has passed and the greenhouse has been ventilated. If entry before the interval has passed is unavoidable, the protection used by the applicator is worn.
Line 83 of Annex 1 of the vocational training regulation lists "work involving the use of agricultural pesticides". If the workplace is in the hazardous or very hazardous class, the vocational training certificate of the worker carrying out the spraying is required before they are hired. For preparing and storing pesticides and the symptoms of poisoning, see our article on safety in pesticide application.
Greenhouse heating and carbon monoxide
In winter and the transitional seasons, greenhouses are heated with boilers, hot air generators or direct-fired heaters. In some greenhouses, burners are also used to provide carbon dioxide enrichment for plant growth. When combustion is incomplete or the flue connection is faulty, carbon monoxide (CO) spreads into the greenhouse. CO is colourless and odourless; its first symptoms, headache, dizziness and nausea, are often mistaken for tiredness.
To reduce the carbon monoxide risk from greenhouse heating:
- Heater and boiler maintenance and flue connections are checked before the heating season starts.
- CO detectors are used inside the greenhouse and especially in guard or worker rooms adjoining the greenhouse.
- If any worker sleeps or keeps night watch near a heater, this arrangement is addressed separately in the risk assessment.
- In greenhouses heated with solid fuel, combustion chamber doors are not left open and hot ash is not left inside the greenhouse.
For symptoms, detector selection and first response, see our article on carbon monoxide poisoning from heaters.
Greenhouse ergonomics: stooped harvesting and overhead work
Greenhouse ergonomics creates problems at both extremes depending on plant height. With low crops such as strawberries, lettuce and seedlings, workers bend or squat for hours. With vertically grown crops such as tomatoes, cucumbers and peppers, the arms stay above shoulder level during plant training, leaf removal and upper harvesting.
Measures:
- For low crops, wheeled stools or trolleys with knee support are used; bending time is broken up through task rotation.
- If a pipe-rail trolley or platform is used for high work, its guardrail, brake and safe movement on the rail are checked. Height is not increased by placing crates or chairs on the trolley.
- Full harvest crates are not lifted from the floor; a crate trolley or a stand at waist height is used.
- The weight of full crates is assessed together with lifting frequency. For the calculation method, see our article on how much weight can be lifted.
The wet floor and irrigation system of a greenhouse must be considered together with electricity: pump and fan panels are protected from moisture, the residual current device is tested regularly and extension leads are kept away from wet floors.
Training, first aid and emergencies inside the greenhouse
A significant proportion of greenhouse workers start seasonally and enter a hot, enclosed environment with pesticides within the same week. The timing of training is therefore as important as its content. Under Art. 7 of the 2026 regulation on OHS training, induction training is given before work starts, lasts at least 2 hours, and is delivered face-to-face and with practical elements. For a greenhouse, this training should cover at least the following: the meaning of the spraying warning sign and not entering a closed greenhouse, signs of heatstroke and the water and break routine, the location of heaters and the CO detector, the assembly point and who to call in an emergency.
Reaching a worker who is injured or faints inside long greenhouse blocks takes time. The number of first aiders is set at one for every 20 workers in less hazardous, every 15 in hazardous and every 10 in very hazardous workplaces; the distribution of first aiders across shifts and blocks should ensure that someone is reachable in every greenhouse section. During the hot season, water for cooling and a shaded area are kept ready alongside the first aid kit.
Greenhouse risks in a single table
| Hazard | When does it increase? | Key measure |
|---|---|---|
| Heat stress | Summer midday, high humidity, heavy work | Working hours, shading, water and breaks, acclimatisation |
| Pesticide vapour and residue | Fogging, fumigation, early re-entry | Warning sign, re-entry interval, suitable PPE |
| Carbon monoxide | Winter, poorly maintained heaters, night watch | Maintenance, flue checks, CO detector |
| Bending and reaching | Harvesting low crops, tending vertical crops | Stools, rail trolleys, task rotation |
| Manual handling | Full crates, fertiliser and pesticide packaging | Crate trolley, stacking at waist height |
| Electricity | Wet floors, irrigation and fan systems | Moisture-protected panels, residual current device |
Check your greenhouse's hazard class according to the activity code in its SGK (Social Security Institution) registration; the class determines all obligations, from specialist and physician time to training hours. The OHS obligation calculator shows the required times for your number of workers. When carrying out risk assessments for agricultural businesses in Bursa and the surrounding provinces, we plan heat stress and spraying arrangements according to the seasonal calendar.
Frequently Asked Questions
Is there a temperature limit for working in a greenhouse?
The legislation has no fixed value saying "no work above this temperature". The Workplace Buildings and Annexes Regulation requires the ambient temperature to be suitable for the work and refers to the TS EN 27243 standard for assessment. The assessment is made together with humidity and the physical demands of the work.
When can a greenhouse be re-entered after spraying?
After the re-entry interval on the product label has passed and the greenhouse has been ventilated. If entry before the interval has passed is unavoidable, the protective equipment used by the applicator is worn and the entry is kept short.
Is a CO detector necessary for a greenhouse heater?
What is mandatory is that the risk is controlled: in an enclosed space where combustion heaters are used, the risk assessment must address carbon monoxide and specify the control measure. A detector is the most practical measure, giving a warning before symptoms begin.
Who can carry out spraying in a greenhouse?
Workers trained in this area who know the product, its risks and the protective equipment. If the workplace is in the hazardous or very hazardous class, a vocational training certificate for the use of agricultural pesticides is also required.
A risk assessment that identifies and scores hazards on site, links each measure to an owner and a date, and has a clear renewal schedule.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.