Answers on choosing, fitting and looking after the filters, covers, chargers and other parts of a powered air respirator system for welders.
How do I work out which filter or spare part fits my powered respirator?
Start with the data plate on the blower unit and the user manual, which list the filters and parts approved for that exact system. Then compare the markings and part number on the old filter or part, and note the filter type and class printed on it.
Use parts from the original manufacturer wherever you can. The HSE advises this because genuine replacements keep the equipment performing as originally intended and offering the protection the maker states. A part that only looks similar may not seal properly or give the same airflow, so if you are unsure, check with the maker or our team before ordering.
What does a particle pre-filter do, and when should it be changed?
A pre-filter is an easily replaced outer layer that catches the larger dust and debris before it reaches the main particle filter, so the main filter lasts longer. Most makers describe it as a routine consumable and it is usually changed more often than the main filter.
Change it when it looks visibly dirty, clogged or damaged, or when the manual says so. There is no single interval, because it depends on the welding process, the material, the dust in your workshop and the maker's instructions. A clogged pre-filter can also reduce airflow, so do not wait for the low airflow alarm.
What is a spark protector and why is it fitted?
A spark protector is a mesh or similar guard that sits in front of the filters in a welding powered respirator. Its job is to stop hot spatter and sparks reaching the filter material, which could otherwise be damaged or burned.
Inspect it regularly for holes, heavy clogging or damage, and replace it straight away if it is damaged, because a damaged guard no longer protects the filter behind it. Always check the manual for the correct way round and the correct position in the filter stack, as it varies between systems.
What does a carbon filter add, and do I always need one?
A carbon filter layer is generally used to help with gases, vapours and odours that a particle filter alone does not deal with. Whether you need one depends on what you are exposed to, such as welding gases, coatings, cleaning solvents or other fumes, so it comes down to your COSHH risk assessment and the safety data for the materials involved.
Carbon filters have limits and can become saturated, so follow the maker's guidance on how they are used and how long they last. Never assume a filter protects against a hazard unless the maker's markings and manual say it does.
How can I tell when the main filter needs replacing?
The HSE explains that filters have a limited capacity or can become clogged, making breathing difficult, so replaceable filters should be changed when necessary. In a powered system, the signs are usually a low airflow warning, a shorter battery run time than before, or a filter that is visibly loaded, wet or damaged.
Check the airflow and battery before every shift, following the manual. If the system will not meet the minimum airflow, do not use it until it has been examined and repaired. Also note any shelf life or replacement period the maker gives, even for unused filters.
Do filters need to match a protection class for my helmet?
Yes. Helmets and hoods that take air from a blower are loose-fitting powered respirators, and they are classed by how much unfiltered air leaks in. The classes are TH1, TH2 and TH3, with TH3 allowing the least leakage. The helmet, blower and filters are approved together, so a filter must be one the maker specifies for that system.
The class and the filter type are marked on the equipment and in the manual. Which level you need depends on the fume and your risk assessment, so do not swap in a different filter type just because it physically fits.