decision would be based on a risk assessment, what material you would be cutting / drilling etc and the properties of that material.

There is no law as such but the point of extraction is to reduce the dust down to acceptable levels and comply with COSHH. Bags just do not do this hence the need for powered suction and M class filters. Take a look at this:- http://www.hse.gov.uk/pubns/cis69.pdf

COSHH is always about hazard control, the hierarchy of control and reduction of risk to ALARP, especially where carinogens and asthmagens are concerned (some wood dusts). Assess each tool or activity qualitively on the risk / quantity of dust released by basic observation first. Hand drills, planes, depending on type and duration of use may not produce much in the region of inhalable dust, and could be controlled merely by good general ventilation (and good house keeping - though try to avoid sweeping). This could be backed up by actually measuring exposures to the dust. Saws, grinders (for wood!? or sanders?) and circular saws are likely to generate much more inhalable (and respirable) dust and ejected at higher speed. On-tool extraction is available for some of these or you could use properly designed local exhuast ventilation - where on-tool extraction is not available. Relying on general ventilation in these cases is unlikely to be sufficient unless the scale of use is very low. I presume you have read: http://www.hse.gov.uk/woodworking/wooddust.htm Clarification on the above post: There is no reason for dust masks to always be worn. Especially if you can demonstrate good control with ventilation. To quote the HSE: "RPE is no substitute for controlling the dust at source and you should only use it as additional protection [such] as a temporary measure where engineering controls are being developed and/or modified. All dusts can now be considered as being hazardous, even what were previously called "non-hazardous" or nusiance dusts. But wood dust hasnt fallen into this category for a long time due to asthma and carcinogenicty links. So to answer the original question. Local exhaust ventilation is likely required for some of your tools and tasks. The HSE has advised M class filters as a minimum for on-tool extraction (http://www.iosh.co.uk/~/media/Documents/Networks/Group/Construction/HSE_Discussion_Document_On-tool_extraction_in_Construction_Industry.ashx) however if you could demonstrate control via other means (Local ventilation NOT masks!) you may be able to not have to retro-fit it to your tools, backed up by breathing zone measurements and observation.