COSHH Assessment for Spray Painting: A Practical Guide for UK Tradespeople

Spray painting is one of the higher-risk tasks a tradesperson can carry out. Atomised paint creates airborne droplets and vapours that penetrate deep into the lungs, and many modern coatings contain substances capable of causing serious, permanent harm. Under the Control of Substances Hazardous to Health Regulations 2002 (COSHH), employers and self-employed contractors must assess the risk before work starts — not as a paperwork exercise, but as a genuine evaluation of what could cause harm and how to prevent it.

---

Why Spray Painting Demands a Careful COSHH Assessment

When paint is sprayed rather than brushed or rolled, exposure increases dramatically. The spray mist suspends fine particles in breathing air, and volatile organic compounds (VOCs) evaporate rapidly at the point of application. The two main hazard categories are:

• Solvents — found in most solvent-borne paints, lacquers and primers. Repeated exposure can damage the liver, kidneys and nervous system. Acute exposure causes dizziness, nausea and impaired judgement.
• Isocyanates — the reactive curing agent in two-pack polyurethane (2K) paints, widely used on vehicles, plant, steelwork and timber. HSE identifies isocyanates as the leading cause of occupational asthma in the UK. Once sensitised, a person may react to even trace concentrations for the rest of their life. There is no cure.

Both categories have Workplace Exposure Limits (WELs) set in EH40, but WELs are a legal ceiling, not a safe target. Your duty under COSHH is to reduce exposure to as low as reasonably practicable.

---

Step-by-Step: Carrying Out the Assessment

1. Identify the Substances Involved

Gather the Safety Data Sheet (SDS) for every product you will use — base coats, primers, hardeners, thinners and cleaning solvents. Check Section 2 (hazard identification) and Section 8 (exposure controls) of each SDS. Note any WELs and look specifically for the words isocyanate, diisocyanate or the prefixes HDI, MDI or TDI.

2. Assess Who Is at Risk and How

Consider:

• The operative doing the spraying
• Anyone in the same enclosed or partially enclosed space
• Bystanders on-site who may drift into the overspray zone
• Re-entry into the area before adequate ventilation

Inhalation is the primary route of exposure. Skin absorption and eye contact are secondary but significant — isocyanates can also trigger asthma through skin contact.

3. Evaluate the Exposure

Ask: how long is the task, how well ventilated is the space, and how much product is being applied? A single day's brush-out in the open air carries very different risk from a week of 2K spraying inside a vehicle workshop or site cabin.

---

Controls: Apply the Hierarchy

Eliminate or substitute first. Can you use a water-borne, lower-VOC product that achieves the same result? Modern water-borne coatings have improved significantly and may remove the isocyanate risk entirely. If substitution is genuinely not practicable, document why.

Engineering controls come before PPE. These are the most reliable because they do not depend on operator behaviour:

LEV systems must be examined and tested at least every 14 months under COSHH regulation 9, and records kept for at least 5 years.

Administrative controls include restricting access during spraying, planning work to limit the number of people exposed, scheduling spraying for times when the site is least occupied, and ensuring adequate drying/ventilation time before re-entry.

PPE is the last line of defence — not the first. For isocyanate work, HSE is explicit: a standard dust mask or even a half-face respirator with incorrect filters will not provide adequate protection. Requirements are:

• Respiratory protective equipment (RPE): For isocyanates, supplied-air or powered air-purifying respirators (PAPRs) with appropriate filters are typically required. Half-face respirators with A/P filters may be acceptable for very short, low-exposure tasks only — check the specific WEL and product SDS. RPE must be fit-tested where a face seal is required (INDG479).
• Skin and eye protection: Nitrile gloves, coveralls and goggles or a face shield to prevent skin sensitisation.
• RPE maintenance: Inspect, clean and store RPE correctly; replace filters according to the manufacturer's schedule.

---

Isocyanate-Specific Requirements

HSE's guidance on isocyanates (published with support from EH40 and HSG258) sets a clear expectation: anyone working with isocyanate-containing products must receive specific training before starting. This covers the health risks, correct use of controls and what to do in an emergency. This is not optional.

---

Health Surveillance

Where employees are regularly exposed to isocyanates or other respiratory sensitisers, COSHH regulation 11 requires health surveillance — typically an initial baseline questionnaire followed by periodic checks by an occupational health professional. Surveillance records must be kept for 40 years.

---

Recording the Assessment

If you employ five or more people, you must record the significant findings of your COSHH assessment in writing (COSHH reg 6). In practice, recording it regardless of workforce size is sound evidence that you have actually done the work. Your assessment should be reviewed whenever the product, method or conditions change, and at least annually for high-hazard tasks like isocyanate spraying.

A COSHH assessment for spray painting is a standalone document focused on substance risk. Where it forms part of a broader piece of work, it will typically sit alongside a method statement within a RAMS pack — but the COSHH assessment itself addresses the substance hazards specifically, not the general task sequence.

---

Getting this assessment right protects your health, the health of people around you, and demonstrates to clients and principal contractors that you are operating to the standard the law actually requires.