COSHH: The Acronym Every Employer Should Understand

From acronym to action

The word that does the heavy lifting in COSHH is control. The regulations do not simply ask you to notice that a substance is hazardous - they ask you to prove you are keeping exposure below a level that protects health. For many airborne substances that level is set by a Workplace Exposure Limit, or WEL. These are the GB occupational exposure limits approved by the HSE and published in the guidance document EH40/2005, and the list is legally binding under COSHH. A WEL is a concentration of a substance in the air, averaged over a set period, and your controls need to keep exposure at or below it.

Some substances get stricter treatment still. Where a substance is classified as a carcinogen, a mutagen or an asthmagen - and flour dust sits in that sensitiser category - you cannot simply aim for the limit. You must reduce exposure to as low as is reasonably practicable, the principle often shortened to ALARP. That is a higher bar, and it is one reason good engineering controls matter so much. You cannot train your way out of a dust problem or rely on a mask to do a job that ventilation should be doing.

This is where a proper COSHH assessment earns its keep. It is not a tick-box exercise but a structured look at what you use, who is exposed, how badly and for how long, and what you are going to do about it. If you have never seen one done well, it is worth reading how COSHH assessments should actually be done - the difference between a generic template and an assessment grounded in your real processes is the difference between paperwork and protection.

The same logic applies to dust-heavy environments beyond the kitchen. In trades where fine particulate is the hazard, the engineering controls carry the whole burden of keeping people safe - and the consequences of getting it wrong are severe. The industry's hard lessons about silica dust and the health risks every site should know are a stark reminder that a substance you cannot easily see can still cause irreversible harm years down the line. Whether the dust is silica, wood or flour, the COSHH principle is identical: control it at source, and check that the control is working.

Why extraction and LEV sit at the heart of COSHH

When you follow the hierarchy of control down from elimination and substitution, you land on engineering controls - and in a commercial kitchen or workshop, that means your extraction system and any local exhaust ventilation. LEV is the equipment that captures contaminated air at or near the point where the hazard is generated, before it reaches anyone's lungs. A kitchen canopy drawing grease-laden vapour away from the cooking line is doing exactly this job, and so is a dedicated extraction arm over a dusty or fume-producing process.

Because LEV is a control measure, COSHH does not let you fit it and forget it. Regulation 9 requires that LEV systems undergo a thorough examination and test - often shortened to a TExT - at intervals not exceeding 14 months. That 14-month figure is a maximum, not a target: it exists to give a two-month scheduling buffer around an annual cycle, so a system tested in the same month each year stays comfortably compliant. Higher-risk processes demand far more frequent checks. Certain processes listed under Schedule 4 of COSHH, including wood dust and welding fume extraction, must be examined at least every six months, precisely because the substances involved carry known links to nasal cancer and serious respiratory disease.

A thorough examination is more than a quick look. A competent examiner - typically someone trained to the HSE guidance HSG258 and holding a recognised qualification such as the BOHS P601 - will measure airflow and capture velocities, check duct velocities, assess filter condition and fan performance, photograph the installation and review whether the system is genuinely controlling exposure to the level your assessment assumed. The resulting report tells you not just that the system runs, but that it protects. Records of these examinations must be kept for at least five years, and they are among the first things an inspector will ask to see.

Understanding COSHH, then, is really about joining the dots. The acronym names the law; the WELs and EH40 set the numbers; the hierarchy of control decides your approach; and LEV testing is the evidence that the engineering controls you have chosen are still doing their job. Miss any link in that chain and the protection quietly stops working - usually without anyone noticing until harm is already done.