Zeta Fresh Air G201X w/ PFU PAPR Parts FAQs
Answers on the filters, battery parts, headgear and other spares for a powered air respirator used with a welding helmet, and how to pick the right ones.
What do P3 and TH3 markings mean on a welding respirator filter?
P stands for particle filter and the number shows efficiency. The HSE describes P3 as high efficiency. Filters that are also usable with powered respirators carry a TH mark for hood or helmet devices, and TM for mask devices.
The HSE lists powered hood and helmet classes TH1, TH2 and TH3, with protection factors of 10, 20 and 40. For arc welding the HSE says to choose powered or air-fed equipment with a protection factor of at least 20. Particle filters do not trap gases or vapours, so always check the marking against the hazard.
When should I change the particle filter in my powered respirator?
Filters have a limited capacity and can clog, so the HSE says replaceable filters should be changed when necessary. For powered hood and helmet filters it says to change them as the manufacturer instructs, so there is no single interval that suits every unit.
Typical signs include a filter or low-airflow alarm, an indicator, a shorter battery run time, or visible damage or wetness. Check your manual for the signs on your unit. Never keep working if the fan stops or the airflow falls: leave the work area and sort the problem out first.
How do I check the airflow, and why does it matter?
A powered helmet protects you by blowing enough clean air across your face to keep contaminated air out. If the airflow drops, that protection drops with it.
The HSE lists checking battery charge and flow rate as a key maintenance task for powered devices, and says to leave the work area at once if the fan stops or the flow falls. Most units have a flow meter or indicator, or an alarm, so use the method in your manual, with a fully charged battery and a clean, correctly fitted filter, before each use.
Does an odour pre-filter protect me from welding gases?
Not on its own. The HSE explains that particle filters do not trap gases or vapours, and gas filters do not protect against particles. Where both are needed, a combined filter marked for both is used.
An odour pre-filter is usually intended to reduce nuisance smells and should not be treated as protection against a gas hazard unless the maker's markings and instructions say so. Whether gas protection is needed depends on your process, materials and risk assessment. Check the markings on the filter and the manual, and ask the maker if in doubt.