HI Jackie
Type 'M's' are foer silica as well as 'H' type ones. These are only recently onto market so not all WorkSafe info wil be up to date. To play safe always check with the manuafacturer (quick email) if it will be suitbale for what you want. I had a recent chat around type M's with Switerland and they came back with the info I needed to make a decsion on it.

Hi Derek

According to WorkSafe https://worksafe.govt.nz/topic-and-industry/dust/silica-dust-in-the-workplace/ or
file:///C:/Users/GJG/Downloads/WKS-17-Dust-silica-dust-in-the-workplace%20(1).pdf

"Use an H-class vacuum cleaner in accordance with
Standard AS/NZS 60335.2.69, fitted with a filter
that can achieve an efficiency of 99.995% (eg H14
HEPA filter complying with Standard AS 4260)."

An M-class vacuum cleaner can have a H14 hepa filter installed but it is still an M-class vacuum cleaner

HI Jackie

Agree, but remember this is only gidnace towards good practice not a must do. If you can prove that an alteernatiive works as well then it can be used. This is the meaning of good practice and not best, ie situation and technolgy are always adavncing and we can't expect worksafe to updatinig their guidelines every week, so it falls to us to do our checks in the background to make sure that we have teh information to show that an altewrnative can be used and wrok successfully.

Cheers