I'm looking for some guidance on exposure monitoring in a metalworking environment.

We prep a variety of metals in our workshop, but mainly stainless steels, ferritic steels and aluminium..
I'm keen to have some exposure monitoring carried out, particularly for grinding operations where a lot of dust is created and I don't believe it's adequately controlled by the extraction system (Airbench with 1.9m/s  averaged over 1.2 x 063m).

I'm reading throuh EH40 and understand that exposure limits for metal dusts are generally '10 mg.m-3 8-hour TWA of inhalable dust or 4 mg.m-3 8-hour TWA of respirable dust', however what particle size is considered 'inhalable' and 'respirable'? 

Outside of this, does anyone have any reputable contacts for carrying out exposure monitoring for metal dusts and metal working fluids? 

Thanks in advance

A particulate with a size of 10µM considered to be inhalable

A particulate with a size of 5 µM considered to be respirable; capable of reaching the alveoli

A fibre is 5 µM in length & 3 µM diameter.

10uM can be captured by nasal hair

1 M = 1,000 mM = 1,000,000 µM.

But it was a long time ago when undertaking dip so could be corrected

You need a reputable occupational hygienist. BOHS website (consultant lists) = one decent starting point, and competent persons therefrom should be able to determine and confirm efficacy and adequacy of LEV.

Seems doubtful IMO that high velocity grinding dust would be effectively captured by an air table alone - and likely to be evident by the levels of dust on surrounding surfaces!