I think for short durations a dust mask is ok to reuse. There are also FFP3 masks which have removable filters which cost more initially but are a cheaper option in the long run, especially if you are using them frequently.  

Thanks both.

Kurdziel: yes the control measures if we choose this will be regular monitoring of the condition and having a dust free location to keep it in when not worn.

and there are no engineering controls in place or available?

With AK regarding contamination on the inside of the mask

With the lauch of the Unite Unions dust register https://unitetheunion.org/news-events/news/2019/august/unite-launches-silica-register-to-protect-workers-whose-health-could-be-damaged-by-dust-inhalation/ it is likely there will be greater drives to eliminate at source as opposed to wrapping the employee

To answer the question, as long as they are manufactured to be reusable then it is fine to reuse them. The data sheet supplied with the masks should state whether they are reusable or not. The 60 minutes is also to do with the strain it puts on a users lungs when in constant use. You will find must people start getting breathless after 60 minutes with a dust mask on.

That being said, it is important that the masks are checked before use each time. It is up to 60 minutes. It is not a goal. If the mask is contaminated or has been compomised then it should be changed. You also will need to ensure the masks are face fit tested, including the user doing their own quick check each time they put on the mask. The HSE (rightly so) does not accept face masks as an effective barrier if they haven't been face fit tested.

The face fit testing is the stumbling block for most companies. Rememeber stubble or beards will make the mask worse than useless. At least with no mask the user is aware of the risk. With an ill fitting mask they may be inclined to stay longer than is necessary. This is why it is so imporatnt to eliminate the dust at source as much as possible.