Hello LisaC,
I guessing that this is going to be part of your manufacturing process.
Therefore (as we stand now), the equipment must be CE marked if stand alone.
If it forms part of a more complex assembly as in a production line which is linked, then the assembly, must, also be CE marked once completed.
Now the responsibility for this final CE marking is yours as the end-user, unless you place a contract with another company, to ensure this is done.
It's not an option, it's the law. Even if you do the line design and implementation yourselves, you are still legally bound to CE mark the assembly. This is specifically written into the law.
Additionally, there is PUWER Reg 10.
Nothing major is going to change in the next 12-13 months, perhaps 24 as the legislation and standards are UK based. Once the "honeymoon" is over it is doubtful that the equipment standards (as in those published by the British Standards Institute) because the ideas in ISO, the IEC, and CEN/CENELEC is that the EN standards will deviate less and less from the ISO/IEC originals, and there will be more of these international standards.
The UK is NOT leaving ISO or the IEC.
OK, why have I stated all of this?
Because, the Essential Health and Safety Requirements (EHSR's) of the Supply of Machinery Safety Regulations (SMSR), by LAW preclude your hazards as described below.
The LAW says that they must not pose a dust explosion risk, end of story, no i's no buts' no options, it is an absolute requirement, not so far as reasonably practicable.
The same with the emissions of hazardous substances, whilst nitrogen is inert, it is an asphyxiant.
As far as the explosive release of pressure goes, then you have the EHSR's of the Pressure Equipment directive (UK version).
So your simple answer is that unless the equipment is poorly maintained and repaired, then the law says it must not pose these hazards. Additionally, compliance with the law is implicit in any commercial contract, therefore the supplier must comply.
The trouble is they don't and under PUWER Reg 10, your organisation is going to be the one in the firing line.
If you don't have adequate safety engineering & I mean safety engineering, not generic H&S competence in your organisation, then I strongly suggest you contract it in and listen to your advisors.