What Does TH3 Mean? A Guide to Powered Respirator Protection
- Cires-Safe
- 12 hours ago
- 5 min read
Powered respirator ratings confuse a lot of people. Two devices can use a similar filter and still offer very different levels of protection. This guide explains the differences between TH1, TH2 and TH3 system in plain English, so you can choose the right respirator with confidence.
Firstly, what is a “TH” rating?
TH1, TH2 and TH3 are protection ratings for loose-fitting powered respirators (PAPRs) under the EN 12941 standard. The higher the number, the more protection the respirator provides.
The key point: the rating measures the whole respirator working together (blower, filter, hose and headtop), not just the filter. TH3 is the highest level available.
Classification | Assigned Protection Factor (APF) | Maximum Recommended Exposure* |
TH1 | 10 | Up to 10 × Workplace Exposure Limit |
TH2 | 20 | Up to 20 × Workplace Exposure Limit |
TH3 | 40 | Up to 40 × Workplace Exposure Limit |
*Subject to risk assessment and manufacturer instructions.
In short, TH3 gives twice the protection of TH2, and four times that of TH1.
Higher TH rating = higher certified protection.
No face fit testing. No problem with beards
This is often the deciding factor. Loose-fitting powered respirators don't seal against the skin, so they don't need face fit testing and can be worn with beards and stubble.
Tight-fitting masks are different. Disposable, half and full-face masks only work if they seal to the skin, which is why HSE requires a fit test for every wearer and why facial hair stops them working. A beard makes a tight-fitting mask unsafe. A loose-fitting PAPR removes that problem entirely.
No face fit testing to arrange, pass, record or repeat.
Works with facial hair, so beards, stubble and religious or personal grooming choices are no barrier to protection.
One solution for the whole team, including workers who could never pass a fit test.
For many organisations, this is the single biggest reason they move to a loose-fitting powered respirator. When that respirator is also certified to TH3, like the AirMask 1000, you get the highest certified protection under EN 12941 alongside the freedom of no fit testing and no clean-shaven requirement.
The filter doesn’t tell you the protection level
A common mistake is judging a respirator by its filter. The filter rating and the TH rating are two different things.
In practice, most TH2 powered respirators use a P2-class filter, while TH3 systems generally use a higher-efficiency P3-class filter. But even the filter alone won't tell you the full story, because the TH rating depends on the complete system, the blower, airflow, hose and headtop all tested together.
So don't compare filters. Compare TH ratings. That's the number that tells you how much protection the wearer actually gets.
Why more organisations choose TH3
TH2 has its place, and your COSHH risk assessment should always guide the final choice. But many UK organisations now standardise on TH3, because it simply does more:
More protection. Twice the APF of TH2, with more margin for peak or variable exposures.
One device for the whole site. Covers more tasks and departments, so you buy and stock less.
Future-proof. If a process changes or limits tighten, you're already covered.
No under-specifying. Less risk of finding out too late that you needed more protection.
How to actually choose: it starts with a risk assessment
The TH rating is only one piece of the puzzle. A suitable COSHH risk assessment should always be the basis for selecting respiratory protection, and it should weigh up:
the specific airborne contaminant and its concentration
the relevant Workplace Exposure Limit (WEL)
task duration and frequency
compatibility with other PPE
comfort, airflow and battery runtime
maintenance, cleaning and communication needs
A useful way to think about it is to picture vehicle crash ratings. Every car on the road is road-legal, but some simply provide more protection than others. The right choice depends on how and where you’ll be driving.
Where this lands in practice
Different ratings suit different environments. Typical use cases include:
TH1: light industrial work, general maintenance, lower-dust environments.
TH2: manufacturing, engineering, warehousing and general industrial processing where exposure exceeds TH1 capability but stays within TH2 limits.
TH3: healthcare, pharmaceutical manufacturing, laboratories, construction, waste and recycling, heavy industry, metalworking, mining, food manufacturing and dust-intensive processes.
A note on form factor: TH3 isn’t just for full-face
Most TH3 powered respirators are full-face or hood and headtop designs. That’s because reaching TH3 in a smaller, lighter half-mask format is hard. The rating depends on the complete system sustaining its performance, and a half-mask gives you far less room to work with.
This matters if comfort, weight or all-day wearability are priorities for your team. A half-mask that’s only certified to a lower TH rating asks you to trade protection for comfort. A half-mask certified to TH3 doesn’t.
The AirMask 1000 is certified to TH3 in both full-face and half-mask configurations, making it one of the only half-mask TH3-certified respirators on the market. That means you can offer the lighter, less intrusive half-mask option without stepping down from the highest certified level of protection available under EN 12941.
The takeaway
TH rating measures the whole respirator, not the filter.
TH3 is the highest level under EN 12941, twice the protection of TH2, 4 times the protection of TH1.
Loose-fitting PAPRs need no fit test and work with beards.
Choose by TH rating and your risk assessment, not by the filter.
Reviewing your respiratory protection programme?CIRES supplies the AirMask 1000, a TH3 PAPR respirator delivering the highest certified level of protection available under EN 12941, in both full-face and half-mask configurations, so your team gets maximum certified protection with a choice of fit. If you want help mapping the right TH rating to your risk assessment, our team is happy to talk it through with no obligation. |
Frequently Asked Questions (FAQs)
What is the difference between TH2 and TH3?
TH2 has an Assigned Protection Factor (APF) of 20 and TH3 has an APF of 40, so TH3 provides twice the protection of TH2 under EN 12941. TH2 is appropriate where a COSHH risk assessment shows exposure falls within its range. Many organisations choose TH3 for the extra headroom and flexibility across varied tasks.
What is the APF of a TH3 respirator?
TH3 has an Assigned Protection Factor (APF) of 40. In simple terms, that means the air inside the respirator is up to 40 times cleaner than the air around you. It's the highest level under EN 12941.
Is TH3 always the right choice?
Not automatically. The correct level of respiratory protection should always be determined by a suitable COSHH risk assessment. TH3 offers the highest certified protection under EN 12941, but a lower rating may be appropriate depending on the contaminant, concentration and task.
Do you need a face fit test for a TH3 powered respirator?
Loose-fitting powered respirators, including TH3 devices like the AirMask 1000, do not require face fit testing because they do not rely on a tight seal against the skin. This is different from tight-fitting masks (disposable, half and full-face), which legally require a face fit test for each wearer under HSE guidance.
Can you wear a TH3 powered respirator with a beard?
Yes. Because loose-fitting powered respirators do not seal against the face, they can be worn with beards, stubble and other facial hair. Tight-fitting masks cannot, because facial hair breaks the seal they depend on, so a loose-fitting powered respirator is often the only effective option for workers with beards.
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