Protection through op-face masks and minimum requirements for respiratory protective equipment

Status:

completed 09/1995

Aims:

In general, op-face masks are used in hospitals to protect patients, doctors and nursing staff in the operating theatre as well as in intensive and premature infant care units against infections. Advertisements for this type of product speak of "excellent filtering performance", "filtering efficiency above 99 percent" etc. The project was aimed to compare the filtering performance of such products with that of filtering respiratory equipment as it is used at industrial workplaces.

Activities/Methods:

The investigations included a total of eleven commercial op- face masks, nine of them mouth cloths and two filtering face pieces. Their efficiency was compared to that of three particle filtering half masks of classes FFP1 and FFP2. The following parameters were determined as described in DIN EN 149: breathing resistance for the inhalation and expiration direction, particle penetration of the filter materials for solid particles in the size range of viruses and small bacteria for the inhalation and expiration direction, total leakage for the inhalation phase (with test persons).

Results:

A comparison of the different op-face masks shows that there is a direct link between the breathing resistance and the particle penetration: The particle penetration decreases while the breathing resistance goes up. No connection could be revealed between the particle penetration and the breathing direction. For some of the op-mouth cloths the expiration resistance turns out to be lower than the inhalation resistance. This is due to the fact the filter material is folded very loosely so that the material surface increases during expiration. The particle penetration degrees of the materials vary between approx. 13% and 94%, the total leakage between approx. 4% and 49%. As the test person-related breathing minute volume in the leakage test is approx. 30 l/min - compared to 95 l/min in the material test - the total leakage of the filter material is clearly reduced in proportion to its particle penetration. Only when the filter material itself has a low penetration degree, the effect of a leakage becomes obvious. Some advertisements are clearly deceptive and hence unacceptable: The particle penetration for a product advertised as "having a filtering efficiency of more than 99%" was measured to be between 70% and 80%. The filtering efficiency of op-face masks has to be improved.

Publications:

OP-Mundschutz. In: Handbuch Atemschutz (Hrsg. Lothar Brauer), ecomed Landsberg/Lech, 61.Erg.Lfg.11/97

Further informations:

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