Posted By Frank Hallett
Hi Jason

Whilst you've obviously done some valuable preparatory work, I'm not convinced that you've gone far enough. Although that depends a lot on a host of other factors - not least the time allocated to install LEV and other engineering measures.

1st, did your sampling take consideration of the actual particle size?

2nd, The type of RPE will have an impact on the overall ability to protect effectively. Half-masks are notoriously less effective than full-face; and disposable tend to be less effective in many areas than re-usable.

3rd, You will have to ensure that all RPE users are properly "Face fit tested" - see earlier thread for much info on this.

Given that you believe that the above all fall within the criteria for FFP2, then you should still get a definitive statement from someone who specialises in this area - and don't rely on the vendors unless the contract with them clearly identifies that they have provided competent professional advice on this topic and everything is in writing.

Frank Hallett

Posted By Adrian Watson
Dear Jason,

As flour dust is known to be a respiratory sensitizer RPE should definitely be the last option in the hierarchy of control; unless it is being used to supplement other controls, for maintenance work, or as a short term stop-gap measure.

As there is no known safe limit of exposure you should provide the best respiratory protections available. As such I would recommend that exposed persons should wear FFP3 Respiratory Protection at the very at all times in areas where there is potential exposure. Furthermore, exposed persons should be subject to routine health surveillance.

Regards Adrian Watson
Registered Occupational Hygienist

Posted By Jason McQueen
Thanks to all those who responded, i'll try and run through the points and questions raised...

Franks 1st post:

1. It didnt mention the particle size specifically but flour dust (if I remember correctly off the top of my head) is 2 microns.

2. Disposable face masks have been ruled out due to the increased difficulty in getting a good fit.

3. Face fit testing will be done.

Adrian's Post: When you say there is no known safe limit of exposure I'm assuming you mean as a sensitising agent to someone who already has susceptibility or am I reading that wrong? The WEL for flour is 10 mg m-3 and although I understand that we should be working towards a zero level of exposure (due to the fact that any amount could lead to/aggrevate occupational asthma given the right conditions). If it isnt reasonably practicable to reach zero exposure, then as long as we can show that we're exposing employees to less than the WEL then surely this is acceptable?

Franks 2nd Post: I'am mindful of the DSEAR issue with this but need to find out what sort of concentration is necessary before the atmosphere could be considered as hazardous.

Maybe I could help by giving some more information regarding the issue. The reason that this has come to light is following the latest dust survey which we had done due an internal change in the fabric of the building.

From this there was one operatives personal sampling results that indicated that over an 8 hour TWA he would be exposed to 300% of the WEL. The task that he was doing wouldnt be done constantly over hours (maybe once an hour) as it involves the mixing of flour for making a pastry batch. Given that it was only this one task which is causing the problem, it makes it easier in terms of controlling in that we could extend the LEV system to cover this working area or provide a portable LEV system that can be positioned directly over the mix (the task cannot be eliminated or replaced with a less harmful substance). But which ever control method we decide upon it is going to take time and capital allocation before we can do anything. Therefore as an interim measure its prudent to supply PPE.

Posted By Adrian Watson
Jason,

In response to your questions: "When you say there is no known safe limit of exposure I'm assuming you mean as a sensitising agent to someone who already has susceptibility or am I reading that wrong?"

Yes, The problems with sensitising agents are two-fold: The first is that the immune response to the substance varies considerably between individuals and cannot be predicted in advance; secondly, the likelyhood of becoming sensitised is dependant upon the protien content of the flour and PEAK exposures to respirable dusts.

As the WEL is an 8 hr TWA and it's based on poor science it's about as much use as teats on a bull!

Whilst it isn't possible to prevent exposures, you have to show that it is not reasonably practical to reduce exposues further; COSHH imposes absolute duties (Dugmore v Swansea NHS Trust). Meeting the WEL would not be a defence in court.

Regarding exposures, comparison with WELs should be made using BS 649. If one operatives personal sampling results indicated that he was exposed to flour dust levels over 300% of the 8 hour TWA WEL.

Remember your duty is not to only to ensure that exposures do not exceed but also to reduce exposures to as low a level as is reasonably practicable. Having regard to that can you change the process to prevent exposures to airborne dust? If not provide LEV and use RPE.

Regarding DSEAR, Flour dust is normally explosive in the region of 50-100 gm.m-3. However, this range is dependant upon the size and dryness of the flour dust. The main problem outside of plant is dust deposits as these may produce secondary explosions if rendered airborne by an in plant explosion.

Regards Adrian Watson