There are several things that should be considered when selecting respiratory protection.
The first thing that should be considered is the suitability of a mask to the contaminant and the nature of the contaminant as it is experienced. For example, there is no point using a dust mask to protect against acidic vapours.
Secondly, you should also bear in mind whether you want disposable masks or reusable respirators.
The advantage of disposable masks is that there are no requirements to keep records under current legislation whereas reusable respirators may be more cost-effective over time and have the added advantage that the same mask can be multi-functional by changing the filter cartridge.