Why your photocopier sometimes smells like ozone and what it means

Where the smell comes from

Office photocopiers create a static electrical charge on the photoreceptor drum as part of the printing process. The charging mechanism — historically a corona wire, in newer devices a charge roller — produces small amounts of ozone as electrical byproduct. Ozone (O₃) is a distinctive sharp clean smell similar to electrical equipment or thunderstorms. The smell is the normal signature of the charging mechanism operating.

When the smell is normal

Light ozone smell during heavy printing or shortly after is normal. Modern office MFPs include ozone filters that capture most of the ozone produced before it reaches the office air, but trace amounts still escape. In a typical office with normal ventilation, the resulting ozone concentration stays well below regulatory exposure limits and well below the level that would cause any health concern.

When the smell suggests maintenance

A strong persistent ozone smell, or a noticeable increase from the device's baseline, suggests one of several maintenance needs. The ozone filter may be saturated and need replacement — most MFPs include this filter as a periodic maintenance item. The corona wire (on older devices) may be dirty and producing more ozone than normal — cleaning the wire restores normal operation. The charge roller assembly may be wearing and producing irregular electrical discharge — this typically requires replacement during a service visit.

Is ozone from a copier dangerous

At the concentrations produced by typical office MFPs in normal office ventilation, no. Modern office MFPs are designed to produce ozone well below occupational exposure limits (the EU OEL for ozone is 0.2 mg/m³ over an 8-hour exposure). The trace amounts that escape past the filter sit well below this limit when ventilation is normal. Concerns arise only in unusual circumstances — a heavily-used device in a small unventilated room with damaged ozone filtration could theoretically produce concentrations approaching the limit, but this is an outlier scenario.

Ventilation guidance

For offices wanting to minimise ozone exposure, the practical guidance is straightforward. Place the MFP in a well-ventilated location rather than a small enclosed room. Keep the ozone filter on the maintenance schedule the manufacturer recommends. Replace the filter promptly when the schedule calls for it. Address any unusual increase in ozone smell quickly — it usually indicates a maintenance need rather than a major problem.

What to do if the smell concerns you

If the ozone smell from your office MFP is strong enough to be uncomfortable or persistent enough to suggest a problem, contact the service provider. The dealer can verify the ozone filter is current, inspect the charge roller or corona wire, and confirm the device is operating within normal parameters. The check is routine maintenance and typically does not produce additional cost beyond the standard service contract.