Key facts
- N99 filters at least 99% of the certification test aerosol.
- N-series filters are not resistant to oil.
- Fit and seal remain as important as filter efficiency.
- N99 filters do not remove gases or vapours.
N99 versus N95
The efficiency number refers to standardized certification testing. The protection actually achieved by a wearer is also limited by face-seal leakage, condition and use.
| Class | Minimum test efficiency | Oil resistance |
|---|---|---|
| N95 | 95% | Not resistant to oil |
| N99 | 99% | Not resistant to oil |
When higher efficiency helps
A hazard assessment may call for a higher-efficiency filter, but breathing resistance, comfort, communication and fit also affect whether the device can be used correctly for the full task.
Limits
- Not for oil aerosols
- Not for gases, vapours or carbon monoxide
- Not for oxygen-deficient or unknown atmospheres
- Not a substitute for source control
Frequently asked questions
Is N99 always better than N95?
It has higher test filtration, but the best respirator is the approved model that matches the hazard, fits the wearer and can be used correctly.
Does N99 require fit testing?
Tight-fitting workplace respirators require fit testing where mandated by the respiratory-protection program.
Can N99 be used around oil mist?
N-series filters are not resistant to oil. A qualified assessment should select an appropriate R- or P-series filter where oil aerosols are present.
Sources
This reference was prepared from the following primary public-health and regulatory sources:
- Filtering Facepiece RespiratorsNational Institute for Occupational Safety and Health
- Respirator Selection and UseNational Institute for Occupational Safety and Health