Choosing respiratory protective equipment (RPE) is not just about picking an FFP2 or FFP3 mask and hoping for the best. In UK workplace safety, one of the most useful numbers for selecting the right level of protection is the Assigned Protection Factor (APF).
APF helps you answer a practical question: “How much can this type of respirator reduce the wearer’s exposure in real use?”
📋 Key Takeaways
- APF is a workplace selection tool, it estimates how much a correctly selected and worn respirator can reduce exposure.
- You use APF alongside exposure limits, such as the UK WEL under COSHH, to decide what level of RPE is suitable.
- APF depends heavily on fit and correct use, a high-rated respirator can perform poorly if it does not seal properly or is worn incorrectly.
- FFP ratings and APF are related but not the same, FFP is a test standard, APF is a practical “in-use” protection assignment.
- Powered systems (PAPR) can increase protection and comfort, especially for long wear and demanding tasks.
What Does APF Mean?
APF (Assigned Protection Factor) is a number that represents the level of protection a class of respirator is expected to provide when properly selected, fitted, worn, and maintained.
In simple terms:
- APF 10 means the wearer’s exposure inside the mask is expected to be up to 10 times lower than the concentration outside the mask.
- APF 20 means up to 20 times lower, and so on.
APF values used in the UK are commonly referenced in guidance such as HSE HSG53 (Respiratory protective equipment at work).
APF is “assigned” because it is not the maximum possible lab performance. It is intended to reflect a realistic, achievable level of protection in workplace conditions, assuming good RPE management.
Why APF Matters (The Practical Reason)
APF matters because it helps you select RPE that is adequate for the hazard level.
In UK workplaces, a common approach is:
- Measure or estimate airborne contamination (dust, fumes, fibres, vapours).
- Compare it to the Workplace Exposure Limit (WEL) where applicable.
- Decide what reduction factor you need.
- Select RPE with an APF that meets or exceeds that requirement.
A quick calculation example
Let’s say:
- The airborne level of a substance is 100 mg/m³
- The WEL is 10 mg/m³
You need to reduce exposure by:
100 ÷ 10 = 10
So, you would typically look for RPE with APF 10 or higher (and still ensure correct filter type, fit testing, maintenance, and other controls).
APF vs FFP Ratings: What Is the Difference?
People often mix up FFP2 / FFP3 and APF. They are connected, but they are not the same thing.
- FFP rating (EN 149) is a product standard based on lab testing and requirements like filter penetration and total inward leakage under test conditions.
- APF is a selection number used to indicate expected protection in the workplace for a class of device.
Mask Comparison
| Feature | FFP2 | FFP3 |
|---|---|---|
| Typical UK APF (filtering facepiece) | 10 | 20 |
| Common uses | General dusts, some aerosols | Higher hazard dusts, fibres, some higher-risk tasks |
| Fit dependency | High | High |
APF values shown are commonly used in UK guidance for disposable filtering facepieces, suitability still depends on the specific hazard and risk assessment.
Typical APF Values You Will See in the UK (Overview)
APF depends on respirator type and whether it is tight-fitting (needs a face seal) or loose-fitting (hood/helmet).
Here is a general overview commonly used in UK RPE selection:
| RPE Type (Typical Category) | General APF Range (UK guidance) | Notes |
|---|---|---|
| Disposable filtering facepiece (FFP2) | 10 | Tight-fitting, fit is critical |
| Disposable filtering facepiece (FFP3) | 20 | Tight-fitting, fit is critical |
| Half mask with replaceable filters (e.g. P3) | 20 | Tight-fitting, requires fit testing |
| Full face mask with replaceable filters | 40 | Tight-fitting, often better seal and eye protection |
| Powered respirator hood/helmet (PAPR, TH classes) | Often up to 40 (depends on class) | Loose-fitting options can suit facial hair, still must be compatible with task and hazard |
APF is not a guarantee of protection for every wearer in every situation. It assumes:
- the correct RPE type for the contaminant (particle vs gas vs combination),
- the respirator is correctly fitted (and fit tested when tight-fitting),
- the equipment is worn correctly for the whole exposure period,
- filters are correct and changed on time,
- the RPE is maintained and stored correctly.
If the atmosphere may be oxygen deficient or immediately dangerous to life or health, you may need supplied-air or breathing apparatus, not a negative-pressure mask.
What Can Reduce Real-World Protection (Even With a High APF)?
APF is only meaningful if the RPE programme is solid. Common reasons protection drops in real use include:
- Poor fit or wrong size
- Facial hair on tight-fitting masks (stubble can be enough to break the seal)
- Incorrect donning and adjustment
- Wrong filter type (for example, using particulate filters when vapour filters are required)
- Clogged or saturated filters
- Damage, worn valves, degraded seals
- Removing the mask in the contaminated area, even briefly
If you need the benefits of higher protection but struggle with comfort, heat, glasses fogging, or long shifts, a powered air system (PAPR) can be a strong solution because it delivers filtered airflow and can reduce breathing resistance.
How to Use APF When Choosing RPE (A Simple Checklist)
Benefits
- Start with the hazard: is it dust, fumes, fibres, biological aerosol, solvent vapour, or mixed?
- Work out how much reduction you need: airborne level ÷ WEL (or other target level).
- Choose the right RPE type: disposable, half mask, full face, powered.
- Confirm compatibility: other PPE, goggles, welding helmet, face shields, communication needs.
- Plan the “supporting system”: fit testing (if required), training, maintenance, filter change schedule.
Product Recommendations (Based on APF-Driven Selection)
Below are a few examples from our range that match common APF-related needs, from disposable protection up to powered systems.
Alpha Solway 3020 FFP2 Face Mask – Box of 20 – Expiry 12/2026
A quality FFP2 disposable respirator option, often selected where an APF 10 class is suitable for the assessed dust or aerosol risk, assuming good fit and correct wear.
3M Front-Fitting Reusable Full Face Mask FF-602F (Medium)
A full face reusable respirator is commonly chosen when you need a higher protection class than disposables can reliably deliver, plus integrated eye protection for certain tasks. Suitable filter selection is essential (particle vs gas vs combination).
3M Versaflo TR-315E+ Powered Air Respirator Starter Kit
A powered air respirator (PAPR) starter kit for users who want improved comfort for longer wear, reduced breathing resistance, and a system approach that can help achieve strong practical protection when correctly configured.
APF and Compliance: Where It Fits in UK Safety Duties
APF is commonly used as part of demonstrating that RPE selection is suitable under:
- COSHH (Control of Substances Hazardous to Health)
- HSE guidance such as HSG53
- Your broader risk assessment and hierarchy of control (elimination, substitution, engineering controls, then PPE/RPE)
APF does not replace the need for exposure control measures like extraction or enclosure, it supports choosing the right RPE when RPE is required.
Final Thoughts
If you remember one thing, make it this: APF helps you choose respirators based on the level of exposure reduction you actually need, not just on whether a product says FFP2 or FFP3.
If you tell us:
- the contaminant (dust, welding fume, silica, solvent vapour, etc.),
- the task and duration,
- whether you have WEL data or monitoring results,
- any fit challenges (facial hair, glasses, long shifts),
we can help you narrow down the safest, most practical options.
