A PAPR draws air through the filter with a blower and delivers it to the breathing zone. That brings two big advantages: breathing takes no effort, and the positive pressure inside the hood resists inward leakage.
Classes TH1, TH2 and TH3
| Class | Total inward leakage | Protection factor |
|---|---|---|
| TH1 | ≤10% | 10× |
| TH2 | ≤2% | 20× |
| TH3 | ≤0.2% | 40× |
Where it is used
- For bearded wearers — a hood does not need a face seal.
- Long shifts in hot environments — the airflow also provides cooling.
- Welding and grinding — the PAPR is usually integrated into a welding helmet.
- Asbestos removal and pharmaceutical production.
One important warning: if the blower stops, most of the protection is lost — a hood does not seal to the face and air enters freely. Charging the battery and checking the flow rate before each shift is therefore mandatory.