Resin Flooring COSHH Assessment: Isocyanates, Solvents & Ventilation Requirements

Table of Contents

• Introduction: The COSHH Challenge in Resin Flooring
• Isocyanates: The Highest Priority COSHH Risk
• Epoxy Resin Systems: Skin and Respiratory Risks
• Solvent-Based Primers and Thinners
• Ventilation: Engineering Control or RPE?
• Health Surveillance Requirements
• What Your COSHH Assessment Must Include
• Frequently Asked Questions

Introduction: The COSHH Challenge in Resin Flooring

Resin flooring installation involves some of the most hazardous chemical exposures in UK construction. Isocyanates in polyurethane systems are the leading cause of occupational asthma in the UK — and sensitisation is permanent and can be career-ending. Epoxy resin systems carry their own sensitisation risks, while solvent-based primers present both flammable atmosphere and narcosis hazards.

The COSHH Regulations 2002 require a systematic approach: identify substances, assess exposure, implement controls, verify controls are working, and provide health surveillance where required. A generic COSHH assessment that simply lists "wear gloves and ensure ventilation" does not meet this requirement for resin flooring products.

This guide provides detailed guidance on each chemical hazard category encountered in resin flooring installation and explains what your COSHH assessment must specifically address.

Browse all trade RAMS templates on the RAMS AI trade hub — covering 22 specialist construction trades.

Isocyanates: The Highest Priority COSHH Risk

Isocyanates are present in polyurethane (PU) resin flooring systems as the hardener or curing component. The most common types in flooring are:

• MDI (Methylene diphenyl diisocyanate) — Used in most two-component PU flooring systems
• HDI (Hexamethylene diisocyanate) — Used in PU-based topcoats and UV-stable systems

The Workplace Exposure Limit (WEL) for MDI is 0.02 mg/m³ (NCO) as an 8-hour time-weighted average and 0.07 mg/m³ as a 15-minute short-term exposure limit. These are among the lowest WELs for any construction product — the limits reflect how dangerous even very low exposures can be to sensitised individuals.

Your COSHH assessment for isocyanates must specifically include:

• The product name and manufacturer, the isocyanate type and concentration (from the SDS), and the NCO content of the product being applied
• The application method (roller, squeegee, spray) — spraying generates aerosols that dramatically increase inhalation exposure compared to roller application. Spray application of isocyanate-containing products requires a higher level of respiratory protection
• The WEL for the specific isocyanate and confirmation that the proposed controls will reduce exposure below the WEL
• RPE selection: for roller application in adequately ventilated areas, A2P3 half-mask; for spray application, PAPR with A2P3 filters
• Skin protection: nitrile gloves, long sleeves, eye protection
• Health surveillance requirement (see below)

The HSE has produced specific guidance on isocyanates: "Controlling isocyanate exposure in the workplace" (HSG262) and COSHH essentials sheet for isocyanate products. Your COSHH assessment should reference these documents.

Epoxy Resin Systems: Skin and Respiratory Risks

Two-component epoxy flooring systems consist of an epoxy resin Part A and an amine-based hardener Part B. Both components carry COSHH obligations:

Epoxy resin (Part A):

• Bisphenol A diglycidyl ether (BADGE) is a Category 1B skin sensitiser
• Repeated skin contact leads to occupational contact dermatitis
• Once sensitised, the individual may react to any epoxy product — sensitisation is irreversible
• Controls: nitrile gloves (minimum 0.2 mm), barrier cream on exposed skin, eye protection

Amine hardeners (Part B):

• Amine-based hardeners are corrosive to skin and mucous membranes
• Some amine hardeners are respiratory sensitisers — inhalation of vapours in poorly ventilated spaces can lead to occupational asthma
• Controls: nitrile gloves, eye protection, face shield when mixing, adequate ventilation

Many epoxy flooring systems also contain reactive diluents (e.g., BGE, BDDGE) which enhance skin penetration and may increase sensitisation risk. Check the SDS for reactive diluents and include them in your COSHH assessment if present at significant concentrations.

Solvent-Based Primers and Thinners

Solvent-based primers are used in resin flooring for penetrating concrete substrates and for improving adhesion to difficult surfaces. They present two hazard categories:

• Fire hazard — Most solvent-based primers have flash points below 21°C (highly flammable) or below 55°C (flammable). Your COSHH and fire risk assessment must specify:
  • Maximum quantity permitted on site at any time (typically one day's supply)
  • Storage in a locked, ventilated COSHH cabinet away from ignition sources
  • No hot works in the area during or for a specified period after primer application
  • Fire extinguisher type (CO₂ or dry powder for Class B fires) within reach during application
• Narcosis and chronic health effects — Solvent vapours at high concentrations cause dizziness, headache, and impairment (narcosis). Prolonged or repeated solvent exposure can cause chronic nervous system damage. Controls: ventilation, organic vapour RPE (A-type cartridge), maximum continuous exposure periods.

Ventilation: Engineering Control or RPE?

The COSHH hierarchy requires that engineering controls (including ventilation) are used in preference to RPE. RPE is supplementary — it is used when engineering controls alone cannot reduce exposure to below the WEL, or as a backup while ventilation is being established.

For resin flooring, adequate ventilation means:

• For roller-applied epoxy and PU systems — a minimum of 5 to 10 air changes per hour in the application area, achieved by natural ventilation (open doors and windows) or forced ventilation (industrial fans or temporary LEV units). Confirm the air change rate with the product manufacturer.
• For spray-applied systems — forced ventilation is almost always required. Natural ventilation is insufficient for spray applications. A dedicated ventilation engineer may be required for large spray application projects.
• For solvent-based primers — solvent vapour must be cleared from the application area before the next operative enters. Ventilation must continue until vapour concentrations fall below the lower explosive limit (LEL) of the solvent.

Your RAMS must specify the ventilation method, the air change rate, and how ventilation adequacy will be confirmed before resin application begins.

Health Surveillance Requirements

The COSHH Regulations require health surveillance for workers exposed to substances that may cause occupational disease, where there is a reasonable likelihood of disease occurring in the context of their work. For resin flooring operatives, this means:

• Isocyanate exposure — Health surveillance is mandatory. The HSE requires that operatives exposed to isocyanates undergo:
  • Pre-placement questionnaire to identify pre-existing respiratory conditions
  • Periodic respiratory health monitoring (questionnaire and, where indicated, lung function tests)
  • Immediate removal from exposure and medical assessment if respiratory symptoms develop
• Epoxy resin exposure — Skin health surveillance is required for frequent users: periodic skin inspection by an appointed person or occupational health nurse to identify early signs of contact dermatitis.

Health surveillance records must be retained for 40 years from the date of last entry (for isocyanates and other respiratory sensitisers). Your COSHH assessment must confirm that health surveillance is in place and identify the occupational health provider responsible.

What Your COSHH Assessment Must Include

• Product list: all chemical products used, SDS references, hazard classifications
• Isocyanate COSHH assessment: product name, isocyanate type, NCO content, WEL, exposure estimation for the application method, ventilation and RPE controls, health surveillance
• Epoxy resin assessment: resin and hardener separately, sensitisation risk, skin and RPE controls
• Solvent assessment: flash point, LEL, narcosis risk, fire controls, organic vapour RPE
• Ventilation specification: air change rate, forced ventilation method, confirmation process
• RPE schedule: filter type, APF, and assigned protection factor for each product and application method
• Health surveillance: provider, frequency, record keeping period
• Spill response and disposal procedures for each product category
• Emergency procedures: eye wash, first aid for chemical burns, evacuation in event of large spill

Frequently Asked Questions

What should we do if an operative develops asthma symptoms while working with polyurethane resin?

Stop the operative's exposure to isocyanates immediately and refer them to an occupational physician. Do not allow them to return to isocyanate work until they have been medically assessed. If sensitisation is confirmed, the operative must not be exposed to isocyanates in any form in the future — even brief low-level exposures can trigger severe reactions in sensitised individuals. Report the case to the HSE under RIDDOR as an occupational disease (Regulation 8) and review your COSHH assessment and controls.

Can we use a water-based epoxy system to avoid solvent exposure?

Yes. Water-based or solvent-free epoxy flooring systems are available and eliminate solvent exposure entirely. They still contain epoxy resin and amine hardeners, so skin and respiratory sensitisation risks remain and must be assessed. However, if your COSHH assessment identifies that solvent exposure is a significant risk (e.g., due to a poorly ventilated application environment), substituting a solvent-free system is a valid higher-order control under the COSHH hierarchy. Document the substitution decision in your COSHH assessment.

How long must the area be ventilated after applying solvent-based primer before other trades can re-enter?

The re-entry period depends on the specific solvent and the ventilation effectiveness. As a starting point, consult the product SDS for the recommended re-entry period. In adequately ventilated spaces (5+ air changes per hour), most solvent-based primers will clear to safe levels within 30 to 60 minutes of completion. In poorly ventilated spaces, you may need to use LEL monitoring equipment before permitting re-entry. Your method statement should specify the re-entry protocol and confirm that the principal contractor will be informed before other trades are permitted to re-enter the area.