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Protect your Lungs: filters and masks

Note that filters only filter the air that actually goes through them. So if your mask does not fit properly and air goes around the edge when you breathe, then that air is not filtered!

Filtering half masks:

Half-face masks cover only the bottom half of the face. There are many factors influencing the choice of filter, so contact your OSH rep before using one. The filter has a limited shelf life, limited working life, and there are specified limits given for each filter type.

The protection factor (beskyttelsfaktoren) indicates how many times the filter can reduce the concentration of a substance. Safe concentration limits for substances must therefore also known. Filters are labelled with: one of eight color codes, one of three classes and a classification number (EN number).

The Institute has seven filtering half masks:

  • Two masks labelled ABEK 1 297 (brown, gray, yellow, green) EN 141 CE 0194 live in the chemical waste room. These must be used with combination filters whenever you are cleaning up spills. They are not for use with organic solvents having a boiling point below 65 degrees C.
  • Two masks live in the Marine Biology Research Centre in Kerteminde and are also used for cleaning up spills.
  • A mask labelled A2 (brown) EN 141 CE 0194 lives beside the histokine automatic tissue-processing machine in the centrifuge room. This is for use with "Exylen", which has a boiling point below 65 degrees C.
Splash masks/dental masks:

These only protect against splashes.

Dust masks:  

These do not protect against gases or vapours, but some types are approved for protection against aerosols. Some types of dust masks are fitted with a valve, which lowers the resistance to exhaling and so is nicer to use. When choosing a dust mask please take into account what it is approved. Approval takes place in three classes:

Class P1 (low power) ... protects from dust to a limited extent. The filter must not be used if the lower safe limit for the pollutant is below 5 mg/m3.

Class P2 (medium power) ... protects against harmful and toxic dust, but not against radioactive dust, bacteria and viruses. Some class P2 filters protect against aerosols.

Class P3 (high power) ... protects as P2, and also against radioactive dust, bacteria and viruses. The mask can be used against both solid particles and liquid aerosols.


The particle filters for filtering facepieces FFP1 and FFP2 have no protection factor given but are equivalent to half masks Classes P1 and P2. Only P3 filters have a protective factor shown, it is 50.

At the Institute we currently have P1 masks with and without valves, both labelled FFP1 (S), whose specification is that they protect against solid aerosols; also P2 masks with valves, labelled FFP2 (S), that protect against solid particles and water based aerosols.


Use of respirators is a last resort, if you think you need to use a respirator, then you should be working in a fume cabinet.

Respirators protect the user only if it is the right choice, if they are maintained properly, and if they are used in the right way.

Respirators and all associated pieces must be CE marked. The label is always followed by the number of the independent testing institute that is responsible for the ongoing control of Personal Protective Equipment.

Last Updated 09.08.2023