Wood dust exposure limits

Exposure limits set the maximum average amount of dust in the air a worker may breathe over a shift. Different agencies set different numbers, and some are legal requirements while others are recommendations. None of them marks a line between safe and unsafe.

The numbers side by side

All values are in milligrams of dust per cubic meter of air (mg/m³), averaged over a full shift unless noted.

STEL is a 15-minute short-term exposure limit.

Notes on each

OSHA (US federal). There is no wood-dust-specific federal limit. Wood dust falls under OSHA’s limits for particulates not otherwise regulated: 15 mg/m³ total dust and 5 mg/m³ respirable dust, as 8-hour averages.¹⁶

OSHA 1989 (history). In 1989 OSHA set wood dust limits of 5 mg/m³ (with a 10 mg/m³ short-term limit) and 2.5 mg/m³ for western red cedar.⁷ A 1992 court decision vacated them, so they no longer apply.²⁸

Cal/OSHA. California sets 2 mg/m³ for soft and hardwoods (short-term limit 5 mg/m³) and 0.5 mg/m³ for western red cedar.¹

NIOSH. NIOSH recommends 1 mg/m³, averaged over up to a 10-hour day in a 40-hour week, and treats wood dust as a potential occupational carcinogen.³

ACGIH. ACGIH recommends 1 mg/m³ inhalable dust for all species except western red cedar, which is 0.5 mg/m³.¹ It also classes oak and beech as confirmed human carcinogens (A1); birch, mahogany, teak and walnut as suspected human carcinogens (A2); and all other wood dusts, including western red cedar, in class A4.¹ It flags western red cedar as both a skin and a respiratory sensitizer.¹

European Union. The binding limit for hardwood dust is 2 mg/m³ inhalable, in force since 17 January 2023 (3 mg/m³ before that). When hardwood dust is mixed with other wood dust, the limit applies to all of it.⁴⁹ There is no EU limit for softwood dust alone.⁴

United Kingdom. EH40 sets 3 mg/m³ for hardwood dust (inhalable) and 5 mg/m³ for softwood dust. If hardwood is mixed with softwood, the hardwood limit applies to all of the dust.⁵

What the terms mean

• mg/m³ is the weight of dust, in milligrams, in one cubic meter of air (a cube one meter on each side). A milligram is a thousandth of a gram.
• Time-weighted average is the average concentration over a work period, usually 8 hours. Because an average can hide short peaks, some limits also come with a 15-minute short-term limit.⁵
• Inhalable dust is roughly the dust that gets into your nose and mouth when you breathe. Respirable dust is the finer part that reaches the deepest parts of the lungs.⁵ Limits for different fractions are not directly comparable.
• Legal vs recommended. OSHA, Cal/OSHA, EU and UK limits are law for employers in those places.¹⁴⁵ NIOSH and ACGIH values are recommendations.³¹

Limits are not safety lines

• Wood dust is classed as a human carcinogen.¹⁰ For substances that cause cancer or asthma, UK law requires exposure to be kept as low as reasonably practicable, even below the limit.⁵
• Research reviews report health effects linked to exposure levels below some of the legal limits above, and more symptoms with higher cumulative exposure.¹¹
• Once someone is sensitized, tiny amounts can trigger symptoms.⁵

Use the lowest limits (around 1 mg/m³) as a rough guide, and aim lower.

What 1 mg/m³ looks like in a hobby shop

Picture a one-car garage shop about 6 m long, 3 m wide and 2.5 m high. That’s 45 m³ of air. At 1 mg/m³, the dust floating in the whole room weighs 45 mg, a small fraction of a gram, spread so thin you can’t see it. Airborne fine dust is normally invisible without special lighting.¹²

So:

• You can’t judge dust levels by eye. A shop that looks clean can be over the limit, and a dusty-looking floor tells you little about the air.
• The dustiest jobs are sawing, routing, turning, sanding, emptying collector bags, and dry sweeping or blowing dust with compressed air.¹² Those are the ones to control first.
• Measuring exposure against these limits means drawing air through a filter with a sampling pump and weighing the dust collected.⁵ For most hobby shops, it’s more practical to assume the dust is significant and control it: see Protection.

Last reviewed 2026-11-07.