COSHH Principles: The 5 Rules That Keep the Chemical Side Honest

Principle 1 — Identify the substance, and the data source

The first principle is the inventory: know what is on the site, and know what each substance is. The data source is the Safety Data Sheet — the 16-section document the supplier provides — and the label. The SDS tells you the hazards, the physical properties, the first aid, the spill response; the label tells you the substance at the point of use. The substance that is not identified is the substance that is not assessed, and the inventory that is not kept is the inventory the inspector finds the gap in.

The identification runs on the change: the new product, the new supplier, the new process — the substance that arrives with the change is the line that is added to the register, and the substance that leaves is the line that is retired. The walkover finds the substance the inventory does not list — the drum with no label, the bottle in the cupboard — and the inventory that is not walked is the inventory that is decoration.

The principle in one line: know what is on the site, from the SDS and the label, and keep the inventory honest on the change.

Principle 2 — Assess the exposure, per substance

The second principle is the exposure, and the exposure has three questions: the route (inhalation, skin, eyes, ingestion), the group (who is exposed, and for how long), and the amount (the concentration, the volume, the temperature, the state). The assessment is per substance, per area, per group — the same solvent in the workshop and in the lab is two assessments, because the exposure and the group are different.

The exposure is what the score is built from, and the score is the likelihood times the consequence on the matrix. The pre-control score is what is there now; the post-control score is what the control moves it to. Write both — the residual is what the review reads, and the ALARP argument is the post-control, written down per substance.

The principle in one line: assess the exposure — the route, the group, the amount — per substance, and write the pre- and post-control scores.

Principle 3 — Control in the hierarchy order

The third principle is the hierarchy, and the chemical order is fixed: eliminate the substance where you can, substitute the less hazardous one, engineer (the local exhaust, the enclosure, the closed system), manage (the procedure, the training, the rotation, the monitoring), and PPE as the last line. The order is the point, and the inspector reads it in that order — the assessment that puts the respirator first and the ventilation last has the hierarchy reversed, and the last line written first.

The substitution is the control the rest of the hierarchy exists because: the water-based for the solvent, the paste for the powder. The assessment that finds the substitution and does not take it has the duty, and the record, the same. The PPE is the last line because it is the control that fails when it is forgotten — the glove that is not worn, the respirator that is not fitted, the suit that is not closed. The PPE is the line of defence, not the first one.

The principle in one line: control in the hierarchy order — eliminate, substitute, engineer, manage, PPE last — and write the control that is actually in place.

Principle 4 — Monitor, and prove the control worked

The fourth principle is the check on the control: the monitoring that proves the exposure the control moved is the exposure the worker is actually in. The monitoring is the air monitoring for the vapour and the dust, the skin check for the dermatitis, the breathing check for the asthma — the health surveillance that hangs off the register line, with the date.

The monitoring is not the assessment; it is the evidence. The assessment says the control moved the exposure; the monitoring proves it. The air sample that comes back under the limit is the proof the exhaust is working; the skin check that finds no dermatitis is the proof the glove is doing its job. The monitoring that is not done is the control that is assumed, and the assumption is the line the investigation reads.

The principle in one line: monitor the exposure — the air, the skin, the breathing — and let the result prove the control, with the date.

Principle 5 — Keep the register, and review on the change

The fifth principle is the register: the site portfolio of the significant substances, one line per substance, with the substance, the CAS number, the area, the main control, the last review and the next review. The register is the document the inspector asks for first, and the health surveillance hangs off it. The register that is not kept is the chemical record that is decoration — the substance that is not in the register is the substance that is not assessed.

The review is per substance, at least every two years, and on the event: the incident, the change to the substance, the change to the process. The review checks the three things — is the exposure still the one assessed, is the control still in place, is the residual still acceptable? The review that finds the control has gone, or the exposure has changed, is the review that starts the re-assessment, not the one that signs it off.

The principle in one line: keep the register per substance, with the review date — and review on the calendar and on the change.

The five principles, as the working method

The five principles are the method, and the method is the sequence: identify the substance from the SDS and the label, assess the exposure per substance, control in the hierarchy order, monitor to prove the control worked, and keep the register with the review date. The sequence is the same at the site and at the bench — the workshop and the lab, the oil field and the garage — and the unit is the substance in every one of them.

The five principles are the chemical side of the risk system, and they are the same logic as the rest: the hazard is the substance, the risk is the exposure, the control is the hierarchy, the record is the register. The difference is the unit and the data source — the substance, and the SDS — and the duty is on the employer under the COSHH Regulations 2002 in the UK, and the OSHA HazCom 2012 standard in the US, where the GHS-aligned structure carries across.

The principles in one paragraph: know the substance, assess the exposure, control in the hierarchy order, monitor to prove the control, keep the register with the review date. The chemical record, in the five rules the duty needs — and the register that is not reviewed is the register that is decoration.