Quick answer
Maintenance can expose workers to chemical residues or substances not encountered during normal operation. Identify those hazards, exchange information and use competent isolation/decontamination and authorised handback arrangements before work. A machine being stopped or apparently empty does not establish that it is free from hazardous substance or stored-energy risks.
Identify non-routine exposure
GB COSHH assessment requirements expressly include activities such as maintenance where exposure may be high. Check the relevant NI framework separately and assess the actual equipment and work.
Consider retained cleaning chemicals, residues, contaminated filters, process materials, unexpected release and substances introduced by the maintenance itself. Avoid assuming normal production precautions cover opened or dismantled equipment.
Exchange information and plan competently
HSE maintenance guidance addresses competent planned work, isolation and safe systems. Provide contractors with relevant process/substance information and obtain their method, substances and control arrangements.
Identify the authorised person for isolation, decontamination and verification. Specialist vessel entry, refrigeration, gas, electrical or other high-risk work needs appropriate qualified arrangements beyond this article.
Use a maintenance chemical-risk checklist
| Stage | Question |
|---|---|
| Before work | What substances/residues and other stored hazards may remain? |
| Preparation | Who authorises the isolation, cleaning/decontamination and confirmation? |
| During work | How are release, contact, contamination and conflicting activities controlled? |
| Waste | How are removed materials, filters and washings managed? |
| Handback | What evidence and checks permit safe return to service? |
A permit, where appropriate, documents a controlled system; its signature is not proof that the equipment is physically safe.
Challenge an unsafe assumption
Illustrative example: an engineer opens a line described as “washed out”, but the chemical identity and completion evidence are unavailable. Pause and obtain the authorised assessment/verification rather than accepting the phrase as proof of safety.
Do not provide improvised flushing, neutralisation or entry instructions. The safe method depends on the substances, equipment and work and requires the necessary competence.
Verify handback and update evidence
Confirm the work is complete, protective measures restored, tools/materials accounted for and relevant checks performed before authorised restart. Assess food-contamination and worker-exposure implications separately but together in the handover.
Record changes, residual restrictions and required instruction. Review the task after unexpected residue, exposure or failed assumptions. Use the existing COSHH assessment guide as a framework, not as a specialist maintenance method.
Next steps
- Identify actual residues and non-routine exposure.
- Exchange information and plan with competent roles.
- Use authorised preparation, work and stop arrangements.
- Verify handback and assess changes before restart.
Read the official practical guidance — Use the current source alongside the procedures for your own business.