Air quality in a small workshop

Extraction at the tool catches most of the dust. What it misses is the finest part — the dust you do not see, which stays in the air for hours after the machine has stopped and settles back on every surface overnight.

What extraction at the tool does

An extractor connected to the sander, saw or router takes the chips and most of the dust at the point where they are made. It is the most important thing in a workshop's air, and nothing replaces it.

What it leaves behind

No extraction catches everything. The very finest particles escape around the edge of the pad or blade, rise with the warm air and stay suspended. In a small room they build up over a working day, and they are the part of the dust that matters most for the people breathing it.

Where an air purifier fits

An air purifier does not compete with extraction at the tool; it cleans up after it. It pulls the room's air through a filter continuously and catches the fine fraction that the extractor let go.

Sizing one to the room

Work out the room's volume: length × width × height. Then compare it with the airflow the purifier is rated for. The aim is for the purifier to pass the room's whole volume of air through its filter several times an hour; the larger the room or the dustier the work, the more airflow you need.

Place it away from the door and away from where the dust is made, so it draws air across the room rather than straight back out. Run it while you work and for a while after you stop.

Habits that help

• Vacuum, do not sweep. A broom lifts the fine dust back into the air.
• Change filters on schedule, not when the suction is already gone.
• Wear a mask for the dustiest jobs, even with good extraction.