Toolbox Talks · Mandatory · Construction
Toolbox Talk — COSHH and Hazardous Substances
A toolbox talk on the risks of hazardous substances on construction sites including safety data sheets and correct PPE.
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.
| Legal basis | Control of Substances Hazardous to Health Regulations 2002 (COSHH) + Management of Health and Safety at Work Regulations 1999 (MHSWR) |
| Scale of the problem | An estimated 12,000 deaths per year in the UK are linked to occupational lung disease, with construction workers disproportionately affected |
| Silica WEL | Respirable crystalline silica workplace exposure limit is 0.1 mg/m3 (8-hour TWA) — one of the lowest WELs for any common construction substance |
| Welding fumes | All welding fume is classified as carcinogenic since 2019 (IARC Group 1). The WEL for welding fume (inhalable) is 1 mg/m3. LEV or RPE is required for all welding, including mild steel |
| COSHH hierarchy | Eliminate, substitute, engineer (enclose or LEV), administrative controls, PPE — applied in that order with PPE as the last resort |
| Enforcing authority | Health and Safety Executive (HSE) |
2. Key Talk Points
The following table sets out the key points that must be covered in a COSHH and hazardous substances toolbox talk. Each point should be related to the specific substances present on site at the time of the talk.
| Talk point | What to cover |
|---|---|
| Silica dust | Respirable crystalline silica (RCS) is generated whenever concrete, block, brick, stone, or mortar is cut, drilled, ground, or scabbled. The WEL is 0.1 mg/m3 — dry cutting exceeds this within minutes. Water suppression and on-tool extraction must be used together for cutting operations. FFP3 RPE (minimum) is required where engineering controls alone cannot reduce exposure below the WEL. Silicosis is incurable and progressive. Health surveillance is required for all workers regularly exposed to RCS. |
| Welding fumes | All welding fume is now classified as carcinogenic (IARC Group 1, 2019). This applies to all welding types including mild steel. The WEL for welding fume (inhalable) is 1 mg/m3. Local exhaust ventilation (LEV) must be the primary control — typically a fume extraction unit positioned at the welding point. Where LEV alone is insufficient (confined spaces, awkward positions), RPE with a minimum P3 particulate filter must be worn. Welding on coated or galvanised metals generates additional toxic fumes that require a separate COSHH assessment. |
| Cement | Wet cement has a pH of 12 to 13 and causes both irritant and allergic contact dermatitis. Chromium VI in cement is a skin sensitiser — once sensitised, the allergic reaction is lifelong. Cement burns from prolonged skin contact can cause full-thickness tissue damage. Waterproof gloves must be worn when handling wet cement. Cement must be washed off skin immediately. Kneeling in wet cement or allowing it to enter boots must be prevented. Barrier cream is not a substitute for gloves. |
| Safety Data Sheets (SDS) on site | A Safety Data Sheet must be available on site for every hazardous substance used or stored. The SDS provides the information needed to complete the COSHH assessment — hazard classification, exposure limits, required controls, first aid measures, and spill response. Workers must know where the SDS file is kept and how to access it. If a product arrives on site without an SDS, it must not be used until the SDS has been obtained and reviewed. |
| RPE and face-fit testing | Respiratory protective equipment (RPE) is the last resort in the COSHH hierarchy, not the first choice. Where RPE is required, it must be suitable for the substance and the exposure level. FFP2 masks are not suitable for silica or welding fume — FFP3 is the minimum. Every tight-fitting RPE (disposable masks, half-face and full-face respirators) must be face-fit tested for the individual wearer using a quantitative or qualitative fit test method. An RPE that has not been face-fit tested provides an unknown and potentially negligible level of protection. Facial hair prevents a seal and means tight-fitting RPE cannot be used — a powered air hood or air-fed visor must be used instead. |
| Health surveillance | COSHH Regulation 11 requires health surveillance for workers exposed to substances with identifiable disease endpoints. On construction sites, this includes workers regularly exposed to silica dust (spirometry and respiratory questionnaire), cement (skin checks for dermatitis), wood dust (nasal and respiratory checks), and other specific substances identified in the COSHH assessment. Health surveillance detects early signs of disease so that exposure can be reduced before irreversible damage occurs. It is not optional and must be carried out by a qualified occupational health provider. |
The COSHH hierarchy must be applied in order — PPE is always the last resort
The COSHH hierarchy requires the duty holder to consider controls in the following order: eliminate the hazardous substance entirely; substitute with a less hazardous alternative; use engineering controls (enclosure, local exhaust ventilation); implement administrative controls (reduced exposure times, job rotation, restricted access zones); and finally, as the last resort, provide personal protective equipment. Jumping straight to PPE without documenting why each higher-level control is not reasonably practicable is a compliance failure. In practice, the HSE expects to see a combination of controls from multiple levels of the hierarchy working together, with PPE providing additional protection where residual risk remains after higher-level controls are in place.
3. Common Mistakes
Using FFP2 masks instead of FFP3 for silica or welding fume
FFP2 masks have an assigned protection factor (APF) of 10, meaning they reduce the wearer’s exposure by a factor of 10. For substances with very low workplace exposure limits — such as respirable crystalline silica (0.1 mg/m3) and welding fume (1 mg/m3) — an APF of 10 is insufficient to reduce typical exposure levels below the WEL. FFP3 masks (APF 20) are the minimum acceptable standard for these substances, and even FFP3 is only suitable for short-duration tasks where other controls (water suppression, LEV) are also in place. For extended exposure, a powered air-purifying respirator (PAPR) with an APF of 40 or higher should be specified. Every RPE must be face-fit tested for the individual wearer.
No on-tool extraction when cutting silica-containing materials
Cutting concrete, block, brick, or stone with a disc cutter, angle grinder, or chop saw generates respirable crystalline silica concentrations that typically exceed the WEL by 10 to 50 times within the first few minutes. Water suppression alone reduces but does not eliminate airborne RCS. On-tool extraction connected to an H-class vacuum captures the fine dust fraction that water suppression misses. The HSE expects both controls to be used together — not one as an alternative to the other. Dry cutting without any controls is one of the most common and most serious COSHH failures on UK construction sites and can result in an immediate prohibition notice.
Not reading or having Safety Data Sheets on site
The Safety Data Sheet (SDS) is the primary source of information about a hazardous substance — its hazard classification, workplace exposure limits, required controls, first aid measures, and emergency procedures. Without the SDS, the COSHH assessment cannot be completed accurately. Every hazardous substance used or stored on site must have its SDS readily available. Workers who use hazardous products must be made aware of the key information in the SDS, particularly the hazards, required PPE, and first aid actions. Products arriving on site without an SDS must not be used until one has been obtained.
Not replacing RPE filters when saturated or at the end of their service life
Respiratory protective equipment with replaceable filters (half-face respirators, full-face respirators) provides protection only as long as the filters are functional. Particulate filters become clogged with dust over time, increasing breathing resistance and reducing airflow. Gas and vapour filters become saturated and allow contaminants to pass through. Disposable masks must be replaced at the end of each shift or sooner if breathing becomes difficult. Replaceable cartridge filters must be changed according to the manufacturer’s schedule or when breakthrough is detected (smell or taste of the contaminant). Using RPE with expired or saturated filters gives a false sense of protection.
Not washing cement off skin promptly
Wet cement has a pH of 12 to 13 — strongly alkaline. Prolonged contact with skin causes chemical burns that can progress to full-thickness tissue damage, particularly when cement enters boots, gloves, or is trapped against skin by clothing. Cement dermatitis (both irritant and allergic) is one of the most common occupational skin diseases in construction. Cement must be washed off skin immediately with clean water. Workers must not kneel in wet concrete or screed without waterproof knee pads. Barrier cream is not a substitute for waterproof gloves and does not provide adequate protection against cement alkalinity.
4. Frequently Asked Questions
Why is respirable crystalline silica so dangerous?▾
Respirable crystalline silica (RCS) particles are small enough (typically 1 to 5 micrometres) to penetrate deep into the lungs and reach the alveoli, where the body cannot clear them. The particles cause an inflammatory response that leads to progressive, irreversible scarring of the lung tissue — a disease called silicosis. Silicosis has no cure and can continue to progress even after all exposure has stopped. RCS is also classified as a Group 1 carcinogen by the International Agency for Research on Cancer, meaning it is a proven cause of lung cancer. The workplace exposure limit of 0.1 mg/m3 reflects its extreme toxicity — this is 40 times lower than the general respirable dust WEL.
Is a Safety Data Sheet required for every product on site?▾
A Safety Data Sheet (SDS) is required for every substance or mixture classified as hazardous under the Classification, Labelling and Packaging (CLP) Regulation. In practice, this covers the vast majority of chemical products used on construction sites, including adhesives, sealants, paints, solvents, cleaning agents, concrete additives, resins, fuels, and many more. The SDS must be in English, must comply with the format set out in REACH Annex II, and must be the current version (check the revision date). The supplier is legally required to provide the SDS free of charge. If a product arrives on site without an SDS, request it from the supplier before the product is used.
What is health surveillance and when is it required?▾
Health surveillance is the systematic monitoring of workers' health to detect early signs of work-related disease. Under COSHH Regulation 11, health surveillance is required for workers who are regularly exposed to hazardous substances that have identifiable disease endpoints — meaning there is a known disease associated with the exposure and a valid method of detecting early signs. On construction sites, this includes workers exposed to respirable crystalline silica (spirometry and respiratory questionnaire for silicosis), cement (skin checks for occupational dermatitis), wood dust (nasal and respiratory assessment), welding fumes (lung function testing), and other substances identified in the COSHH assessment. Health surveillance must be carried out by a qualified occupational health professional and records must be retained for 40 years.
What is a face-fit test and why is it required?▾
A face-fit test determines whether a specific make and model of tight-fitting RPE achieves an adequate seal on an individual wearer’s face. Everyone’s face shape is different, and a mask that fits one person well may not fit another. Without a face-fit test, the actual protection factor achieved is unknown and may be significantly lower than the assigned protection factor stated by the manufacturer. COSHH Regulation 7 and the HSE’s RPE guidance (RPE-APR-04) require that all tight-fitting RPE (disposable masks, half-face respirators, full-face respirators) is face-fit tested for each individual wearer. The test must be repeated whenever a different make or model of RPE is issued, and should be repeated if the wearer’s facial features change significantly (weight gain or loss, dental work, scarring). Workers with facial hair that passes under the sealing surface of the mask cannot achieve a seal and must use a powered air hood or air-fed visor instead.
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