Spray Booths and the Risks Faced by Painters

Wet paint and powder coating: two different risk profiles

Spray booth safety starts with which paint is used in the booth. In wet paint booths, solvent-based or water-based liquid paint is sprayed with a gun; solvent vapour and paint mist form in the air. In powder coating booths, powder charged by an electrostatic gun is attracted onto an earthed part, which is then cured in an oven; a fine, combustible dust cloud forms in the air. Although the hazards of the two systems fall under similar headings, the details of the measures differ.

At automotive supplier plants in Bursa, painting metal parts, body parts and assemblies is a routine step in production. Manufacture of vehicle body parts (29.32.21) is in the hazardous class in the 2025 list. Even if the paint shop is a small department, a significant share of the business's fire, explosion and occupational disease risks is concentrated here. Painter safety should therefore be addressed as a separate heading in the risk assessment.

Spray booth safety in one table

The zone classes in the table are the result of the assessment rather than of the booth itself: the inside of the booth, the exhaust duct and the area around the booth opening are classified separately according to how often an explosive atmosphere forms.

Spray booth ventilation: what to look for

Ventilation is the first measure against both explosion and health risks in the paint shop. Annex I item 2.5.1 of the Regulation on Health and Safety Requirements for the Use of Work Equipment requires equipment with a risk of releasing gas, vapour, liquid or dust to be fitted with systems that contain or extract them at source. On site, the following points are checked:

• Airflow: is the booth operating at the air velocity designed by the manufacturer? Is paint mist escaping from the booth opening?
• Filter condition: the differential pressure gauge (manometer) shows filter clogging. A clogged filter both reduces ventilation and builds up combustible paint deposits.
• Interlock: an interlock that prevents spraying while the ventilation is not running is the most effective safeguard.
• Ducts: paint and powder building up in exhaust ducts are cleaned regularly.
• Periodic inspection: the ventilation installation is inspected by authorised persons at least once a year.

How well ventilation cleans the air the painter breathes can only be seen by measurement. We plan chemical exposure measurements with authorised laboratories and enter the results into the risk assessment. For when measurement is required, see our article on workplaces where exposure monitoring is mandatory.

Explosive atmospheres and electrostatic painting

Art. 5 of the Regulation on the Protection of Workers from the Hazards of Explosive Atmospheres sets an order of priority for measures: first prevent an explosive atmosphere from forming, if that is not possible prevent its ignition, and finally reduce the harmful effects of an explosion. Under Art. 9, the employer classifies places where explosive atmospheres may form and puts warning signs at their entrances; under Art. 10, the employer prepares the explosion protection document before work begins and updates it when significant changes are made. The equipment category to be used in a classified zone is also set in the regulation: category 1 or 2 for Zone 1 or 21, and category 1, 2 or 3 for Zone 2 or 22.

In practice, this means that lighting, fan motors, sockets and sensors inside the booth must be suitable for the zone, and that no ordinary extension lead, phone charger or portable heater is brought into the booth. For the content of the document, see our article on the explosion protection document.

Static electricity is the invisible ignition source in the paint shop. The regulation requires electrostatic discharges to be considered as an ignition hazard and, where necessary, PPE made of suitable material to be provided. In electrostatic painting systems, the paint is charged at high voltage in the gun and attracted to the earthed part; if earthing is poor, charge builds up on the part or hanger and can discharge with a spark. So:

• Part hangers and conveyor hooks are cleaned regularly; paint building up on them breaks the earth connection.
• The booth, gun, hose, buckets and conductive floor are earthed; earthing is measured regularly. For details, see our article on earthing and residual current devices.
• The painter wears conductive footwear; footwear with insulating soles and synthetic clothing that builds up static charge are avoided.
• The distance between the gun and the part is set according to the manufacturer's instructions.

Painter's masks and respiratory protection

The starting point for choosing a painter's mask is the product's safety data sheet; the relevant sections of the sheet state which protection is needed against which substance. For reading the sheet, see our article on the safety data sheet. The general framework is as follows:

• Solvent-based wet paint: a half or full face mask with a combined filter, combining a gas/vapour filter against organic vapour and a particle filter against paint mist. A dust mask does not protect against solvent vapour.
• Two-component paints and varnishes containing isocyanates: isocyanates can sensitise the airways and cause occupational asthma. When spraying these products, supplied-air respiratory protection is preferred.
• Powder coating: a mask with a particle filter; the class is chosen according to the level of exposure. For selection, see our article on dust mask classes.

For a filter mask to work, it must fit the face fully; a beard breaks the seal. The filter replacement interval is set in advance according to usage time and manufacturer information; do not wait until you can smell something. For the general rules of PPE selection, see our article on choosing PPE.

Health surveillance for painters focuses on the respiratory system and skin. In the hazardous class, periodic examinations are carried out at least every 3 years, and the physician may shorten this interval. Tests such as lung function tests have no fixed frequency in the legislation; the workplace physician decides according to exposure. We plan tests with authorised laboratories and health facilities.

Paint mixing area and curing oven

There are two more areas that carry as much risk as the booth. The first is the paint mixing area: in this area, where paint is thinned, mixed and filled into the gun, vapour escapes from open containers and spills occur. The mixing area should be ventilated, only enough paint and thinner for the day's needs should be kept there, containers should be earthed during transfer, and absorbent material should be kept ready for spills. Large stocks are kept in a separate flammable materials store.

The second is the curing oven. Powder-coated parts, and parts painted with some wet paint systems, are cured in an oven. Oven surfaces and parts fresh out of the oven carry a burn risk; workers handling parts wear heat-resistant gloves. In gas-fired ovens, burner maintenance and the discharge of combustion gases outdoors should be checked regularly; a gas leak or poor flue draught can lead to carbon monoxide build-up. Paint residues building up inside the oven can also ignite; include the inside of the oven and its ducts in the cleaning plan.

Cleaning, waste and daily checks

A significant share of paint shop fires arise from failures in cleaning and waste management. The daily checklist should include:

• Are the booth ventilation and interlock working, and is the filter differential pressure in the normal range?
• Are there paint or powder deposits inside the booth and at the duct opening?
• Are solvent rags in a lidded metal container, and is the container emptied at the end of the day?
• Is the amount of paint and thinner in the production area limited to the day's needs, and are drum lids closed?
• Are hangers clean and earth connections sound?
• In the powder coating area, is cleaning done with a suitable vacuum rather than compressed air?
• Are extinguishers in place and close to the booth entrance?
• Are the painter's mask, filter and gloves ready and suitable?

If hot work such as grinding and welding is to be done near the spray booth, a permit is obtained; see hot work permit.

Bursa Sistemer OSGB provides OHS specialist and risk assessment services to production plants in Bursa and the surrounding provinces. Paint shop risks are covered together with the sector's other topics on our automotive supplier industry page; you can use the OHS calendar tool to track renewal dates.

Frequently Asked Questions

We use water-based paint; is there no explosive atmosphere risk?

Water-based paints generally contain less solvent, but that does not mean they contain no solvent. Check the flash point and composition in the product's safety data sheet; if solvent-based products, thinner or cleaning solvent are also used in the same booth, the assessment is made accordingly.

Can an ordinary extractor fan be used in a spray booth?

Fans and motors used in a zone classified as an explosive atmosphere must be of a category suitable for the zone. An ordinary extractor fan can be an ignition source; check the explosion protection document before making any changes.

Which mask should a painter be given?

For solvent-based wet paint, a mask combining gas/vapour and particle filters is used; for powder coating, a mask with a particle filter. For two-component products containing isocyanates, supplied-air respiratory protection is preferred. The final choice is made according to the product's safety data sheet.

Is a spray booth subject to periodic inspection?

The ventilation installation is included in the Annex III tables of the Work Equipment Regulation and is inspected at least once a year unless the standard or the manufacturer's instructions set a shorter period. The internal electrical installation and earthing are also inspected at least once a year.