Is coffee roasting harmful to workers?

Roasting and grinding release substances such as diacetyl, and green coffee dust can affect some people's breathing. With good ventilation, cooling before grinding and local exhaust ventilation, exposure can be controlled. HSE publishes guidance.

How often should roaster ducts be cleaned?

Follow the maker's guidance and your own inspection results. Busy roasteries often clean chaff daily and inspect ducts at intervals measured in weeks or batches.

Extraction and ventilation in a roastery: fumes, dust and fire

The roaster's exhaust carries smoke and chaff out; the room still needs air for the burner and protection for staff from roasting fumes and dust. The rules and the practical design points.

7 min read Updated October 9, 2026

Ventilation in a roastery does three jobs: it takes the roaster's hot, smoky, chaff-laden exhaust safely outside; it supplies air to the burner and the room; and it protects the people working there from fumes and dust. Each has its own design rules.

The roaster exhaust

Follow the maker's duct diameter and maximum run length; long runs and many bends reduce airflow and change how the roaster behaves.
Use materials and clearances suitable for hot exhaust, and keep ducts away from combustible structures. Ask a fire engineer where ducts pass through walls or roofs.
Fit cleaning access points so the whole run can be inspected and cleaned.
Terminate the flue where the exhaust disperses well and does not re-enter your building or neighbours' windows and air intakes.
Keep the chaff collector or cyclone accessible for daily emptying.

Make-up air for the burner

A gas burner needs combustion air, and the exhaust fan removes air from the room. Without enough make-up air, a roaster can draw fumes back or burn poorly. Your Gas Safe engineer will check ventilation requirements for the appliance; tell them about any other extraction in the same room.

Protecting staff: diacetyl and dust

The Health and Safety Executive has issued a safety bulletin on diacetyl, a substance produced when coffee is roasted and released when roasted coffee is ground, especially while still warm. Exposure can cause serious, irreversible lung disease. Great Britain has workplace exposure limits for diacetyl of 0.02 ppm over 8 hours and 0.10 ppm over 15 minutes, published in the HSE's EH40 list.

HSE's bulletin notes that exposure is higher when beans are ground warm, and lower when they are cooled to room temperature first. Practical controls include:

Controls to consider

Let roasted coffee cool fully before grinding
Fit local exhaust ventilation (LEV) at grinders and at open packing of freshly roasted coffee
Keep roasted coffee in closed containers while it degasses, in a ventilated area
Assess the risk under COSHH and record it
Have LEV systems thoroughly examined and tested at least every 14 months, as COSHH requires
Control green coffee dust when tipping sacks; green coffee dust can trigger respiratory symptoms in some workers

Fire

Chaff is light, dry and flammable; ducts collect oily deposits. Most roastery fires start in the cooling tray, chaff collector or ducting. Clean on a schedule, never leave a hot roaster unattended, and keep suitable extinguishers next to the roaster with staff trained to use them. Your fire risk assessment, required under the Regulatory Reform (Fire Safety) Order 2005 in England and Wales, should cover the roaster specifically.

Where Roastnet helps

Questions roasters ask

Is coffee roasting harmful to workers?: Roasting and grinding release substances such as diacetyl, and green coffee dust can affect some people's breathing. With good ventilation, cooling before grinding and local exhaust ventilation, exposure can be controlled. HSE publishes guidance.
How often should roaster ducts be cleaned?: Follow the maker's guidance and your own inspection results. Busy roasteries often clean chaff daily and inspect ducts at intervals measured in weeks or batches.

Official sources

Rules change. These sources were checked on October 9, 2026; always confirm the current position with the body that publishes them before you act.