COSHH · Mandatory · Pre-Construction
COSHH Assessment — Adhesives and Resins
This COSHH assessment covers epoxy resins, polyurethane adhesives, contact adhesives, and other bonding agents used in construction. It addresses skin sensitisation, respiratory irritation from isocyanates, and the risk of occupational asthma. Two-part resin systems require specific mixing controls and adequate cure-time ventilation.
Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. COSHH Regs 2002 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.
| Epoxy resins | Bisphenol A diglycidyl ether (BADGE) is the primary sensitiser. Epoxy resin systems cause irreversible allergic contact dermatitis. Sensitisation can occur after weeks, months, or years of exposure — there is no safe exposure period. Once sensitised, any future contact triggers the reaction. |
| PU resins | Polyurethane resin systems contain isocyanates (typically MDI or HDI) in the hardener component. These are respiratory sensitisers and Group 2A carcinogens. The COSHH requirements for isocyanates apply in full — see also C3 (Paints and Solvents) for detailed isocyanate controls. |
| Contact adhesives | Solvent-based contact adhesives contain flammable solvents (typically acetone, MEK, toluene, or hexane). DSEAR applies for fire and explosion risk. Solvent vapour is heavier than air and accumulates at low level, creating an explosive atmosphere in enclosed spaces. |
| Acrylic / MMA | Methyl methacrylate (MMA) is an irritant with a WEL of 208 mg/m³ (8-hr TWA). Used in structural adhesives, flooring screeds, and repair compounds. Strong odour at low concentrations but health effects occur at higher levels. Can cause respiratory and skin irritation. |
| Skin protection | Nitrile gloves are the minimum standard for handling adhesives and resins. Thickness must be appropriate to the substance (minimum 0.4 mm for epoxy, check SDS for breakthrough time). Latex gloves are not suitable. Barrier cream is not a substitute for gloves. |
1. Epoxy Resins — Sensitisation Risk
Epoxy resin systems are among the most potent skin sensitisers encountered on construction sites. The primary sensitising component is bisphenol A diglycidyl ether (BADGE), which is present in the resin component of virtually all standard epoxy systems. The hardener (amine) component is also a sensitiser and an irritant. Reactive diluents added to reduce viscosity are often more potent sensitisers than the base resin itself. The COSHH assessment must address all components of the epoxy system, not just the mixed product.
Epoxy sensitisation is a type IV (delayed) hypersensitivity reaction. Once a worker becomes sensitised, any subsequent skin contact with uncured epoxy — even in minute quantities — triggers an allergic contact dermatitis reaction. The reaction typically occurs 24-72 hours after contact and presents as redness, swelling, blistering, and intense itching at the contact site. Sensitisation is irreversible: there is no treatment and no desensitisation therapy. A sensitised worker must be permanently removed from all work involving uncured epoxy resin.
Epoxy resins are widely used in construction: structural adhesives, concrete repair compounds, floor coatings and screeds, protective coatings for steel and concrete, grouting of fixings and anchors, fibre-reinforced polymer (FRP) strengthening systems, and waterproofing membranes. The COSHH assessment must identify every product on site that contains epoxy resin and ensure that the controls are adequate for each application.
There is no safe period of exposure before sensitisation occurs
Unlike some sensitisers that require prolonged or heavy exposure before sensitisation develops, epoxy sensitisation can occur after a single exposure, after weeks of exposure, or after years of apparently trouble-free use. There is no predictable threshold and no safe period. Some workers are sensitised within days of first contact; others work with epoxy for years before developing the allergy. This unpredictability means that prevention through strict skin protection must be maintained from the first day of exposure, not relaxed because a worker "has been fine so far." Once sensitisation occurs, even trace contact with uncured epoxy — from contaminated tools, surfaces, or clothing — will trigger a reaction.
2. Solvent-Based Adhesives and DSEAR
Solvent-based contact adhesives are widely used in construction for flooring installation, wall coverings, insulation bonding, and trim fixing. These products contain volatile flammable solvents — commonly acetone, methyl ethyl ketone (MEK), toluene, hexane, or proprietary solvent blends. In addition to the health risks from solvent inhalation and skin contact (covered by COSHH), these products create a fire and explosion risk that must be assessed under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).
Solvent vapour from contact adhesives is heavier than air and accumulates at floor level. In enclosed or poorly ventilated rooms, the vapour concentration can reach the lower explosive limit (LEL) within minutes of application, particularly when large surface areas are being coated. A single spark from electrical equipment, a light switch, a power tool, or static discharge can ignite the vapour, causing a flash fire or explosion. The DSEAR assessment must identify all areas where explosive atmospheres may form, classify them into ATEX zones, and specify the controls to eliminate or manage ignition sources.
| Control area | Requirement | Common failure | Consequence |
|---|---|---|---|
| Ignition sources | All ignition sources must be eliminated from the work area and adjacent areas where vapour could migrate. This includes: electrical equipment (switched off and isolated), hot works (prohibited), smoking (prohibited), mobile phones (not used), static discharge (earthing and bonding of containers). | Electrical equipment left energised in the room. Hot works carried out in adjacent areas without assessing vapour migration. Operatives using mobile phones. Light switches operated while vapour is present. | Ignition of solvent vapour causing flash fire or explosion. Solvent vapour fires in enclosed spaces are extremely dangerous because the fire propagates rapidly through the accumulated vapour layer. |
| Ventilation | Mechanical ventilation must be provided to maintain solvent vapour concentrations below 25% of the LEL (lower explosive limit) at all times. Extraction should be at low level (where vapour accumulates). Natural ventilation alone is rarely adequate for large-area contact adhesive application in enclosed rooms. | No ventilation assessment. Relying on open windows. No monitoring of vapour concentrations. Extraction fans not rated for ATEX zone. | Vapour accumulation to explosive concentrations. Operatives exposed to solvent concentrations exceeding WELs. Non-ATEX-rated fans can themselves become an ignition source. |
| Storage | Solvent-based adhesives must be stored in a fire-resistant store, away from ignition sources, direct sunlight, and heat. Quantities in the work area should be limited to the amount needed for the immediate task. Containers must be kept closed when not in use. | Large quantities stored in the work area. Containers left open. Storage near heat sources or electrical distribution boards. No fire-resistant storage provision on site. | Increased fire load. Increased vapour generation from open containers. Fire in the storage area spreading to the solvent stock. |
| Spill response | Spill kits appropriate to the solvent type must be available. Spilled solvent must be absorbed with inert absorbent material (not sawdust, which is combustible), collected, and disposed of as hazardous waste. Contaminated absorbent must not be left in the work area. | No spill kit available. Solvent spills left to evaporate. Sawdust used as absorbent. Contaminated waste left in the work area. | Rapid evaporation of spilled solvent creating high vapour concentrations. Contaminated sawdust is a fire hazard. Improper disposal creates environmental and fire risks. |
3. Common Mistakes
Not treating two-component resin products as isocyanate hazards
Two-component (2K) polyurethane adhesives and resins contain isocyanates in the hardener component, just as two-pack polyurethane paints do. The same COSHH requirements apply: isocyanate-specific risk assessment, respiratory surveillance, appropriate RPE, and skin protection. Many operatives and supervisors do not make the connection between a "flooring adhesive" or "structural resin" and the isocyanate hazard because the product is not a paint. The COSHH assessment must check the SDS of every two-component product to identify whether it contains diisocyanates.
Inadequate gloves for epoxy resin handling
Epoxy resin penetrates thin disposable gloves rapidly. Standard nitrile examination gloves (0.1-0.2 mm) may provide only 10-15 minutes of breakthrough time for some epoxy formulations. The COSHH assessment must specify the glove type, material, and minimum thickness based on the SDS permeation data. For most epoxy systems, nitrile gloves of at least 0.4 mm thickness are required, and they must be changed at intervals shorter than the breakthrough time. Double gloving (a thin inner glove under a thicker outer glove) is recommended so that if the outer glove is breached, the inner glove provides temporary protection while a new outer glove is donned.
Using contact adhesives in confined or poorly ventilated spaces without DSEAR assessment
Applying solvent-based contact adhesive in a small enclosed room, a bathroom, a cupboard, or any space without adequate ventilation creates an immediate fire and explosion risk as well as a health risk from solvent inhalation. The DSEAR assessment must be completed before work begins. In many cases, the assessment will conclude that mechanical ventilation is required, ignition sources must be eliminated (including isolating electrical circuits in the room), and the work should be planned to minimise the time that containers are open and adhesive is exposed to the air.
Not reading the Safety Data Sheet before using an adhesive or resin
The SDS is the primary source of information on the hazards, exposure limits, recommended controls, and emergency procedures for any chemical product. Many operatives use adhesives and resins without ever seeing the SDS, relying instead on the product label (which provides only summary hazard information) or on past experience with a similar product. Products are reformulated by manufacturers, and a product that was previously low-hazard may now contain different components. The COSHH assessment must be based on the current SDS for the specific product and batch being used.
Disposing of surplus adhesive and resin without procedures
Uncured adhesives and resins (particularly epoxy and polyurethane products) are hazardous waste. They must not be disposed of by pouring down drains, into general waste skips, or onto the ground. Mixed two-component products that are allowed to cure in the container before disposal may generate significant heat (exothermic reaction) and in some cases can self-ignite if the volume is large enough. The COSHH assessment must specify the disposal method for surplus product, contaminated packaging, and contaminated PPE. Waste must be segregated and disposed of through a licensed hazardous waste carrier.
5. Frequently Asked Questions
Which adhesives require a full COSHH assessment?▾
All adhesives that contain substances hazardous to health require a COSHH assessment. This includes: all epoxy resin systems (two-component); all polyurethane adhesives containing isocyanates (two-component); all solvent-based contact adhesives; all acrylic/MMA-based structural adhesives; cyanoacrylate (superglue) adhesives (irritant vapour); and any adhesive whose Safety Data Sheet identifies hazardous components. Water-based PVA adhesives and similar low-hazard products may require only a brief assessment confirming that the risk is low and no special controls are needed, but the assessment must still be carried out. The SDS is the starting point for determining the hazard profile of any adhesive product.
Are water-based adhesives safe to use without precautions?▾
Water-based adhesives are generally lower hazard than solvent-based or reactive resin products, but they are not necessarily "safe" without any precautions. Many water-based adhesives contain preservatives (such as isothiazolinones) that are potent skin sensitisers. Some contain small quantities of organic solvents or co-solvents. The COSHH assessment must check the SDS for the specific product. At a minimum, skin protection (gloves) should be used to prevent dermatitis from repeated skin contact, and the product should be used in adequately ventilated conditions. The claim "water-based = safe" is a simplification that the COSHH assessment must not accept at face value.
What ventilation rate is needed when using contact adhesives in enclosed rooms?▾
There is no single universally applicable ventilation rate because it depends on the room volume, the surface area being coated, the application rate, the solvent type, and the ambient temperature. As a general guide, the ventilation must maintain solvent vapour concentrations below 25% of the lower explosive limit (LEL) at all times (for fire safety) and below the relevant WEL for health protection. For a typical room where contact adhesive is being applied to a floor area, mechanical extraction providing 10-15 air changes per hour at low level is a reasonable starting point, but this must be verified by calculation or monitoring for the specific circumstances. Portable vapour monitors should be used to confirm that concentrations remain within safe limits during application.
How long after applying adhesive or resin should the area be left before re-entry?▾
The re-entry time depends on the product type, the ventilation conditions, and the substance involved. For solvent-based contact adhesives, re-entry should not occur until the solvent vapour concentration has fallen below the WEL, which may take several hours in a poorly ventilated room. For epoxy resins, re-entry is generally safe once the product has cured to a tack-free state (uncured epoxy is the sensitisation hazard, not cured epoxy), but this varies from 4-24 hours depending on the product and temperature. For isocyanate-containing products, re-entry should not occur until airborne isocyanate levels have fallen below the WEL (0.02 mg/m³), which should be confirmed by air monitoring. The COSHH assessment must specify the re-entry criteria for each product and how compliance will be verified.
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