Respiratory Protection

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Evaluating the gas filter service life

The prevention officer or HSE manager must ensure that the gas filters fitted on the respiratory protective equipment protect the employee throughout his/her task.

To do this, they can determine the time after which the gas filter is no longer able to retain the pollutant (toxic gases) against which protection is required: this is the saturation time or breakthrough time (also known as service time). The filter then allows the pollutant through and the wearer no longer breathes fully filtered air.

When using a gas filter, the gas molecules are trapped in the surface pores of the activated carbon as the pollutant-laden air passes through. The filter will progressively become increasingly saturated. The purification capacity of the filter is measured in accordance with a standardized procedure (NF EN 14387 + A1): the filter is subjected to a fixed air flow containing a known concentration of a test gas and its concentration is measured downstream of the filter.
When plotting the concentration of the test gas downstream of the filter, a gradual increase is observed over time until the filter reaches its "breakthrough time", at which point it very quickly becomes saturated.

courbe claquage

This breakthrough time is used to evaluate the actual duration of the protection provided by the gas filter in a working situation.

To evaluate the duration of the protection offered by the gas filter, the prevention officer or the HSE manager can use:

The manufacturer's productsheet and predictive calculation tools (Prémédia, Saturisk etc.)

This theoretical information is useful for pre-dimensioning the prevention device, but is not fully representative of the actual conditions of use since these are only partially known.

cartouche K7 Versaflow

Colorimetric indicators

These end-of-life indicators change color when the concentration of pollutants exceeds the acceptable limit. Their specific nature, the sometimes random time taken for the chemical reaction leading to the color change and the fact that the color change is sometimes difficult to detect mean that these indicators are very rarely used.

cartouche indicateur fin de vie

Destructive laboratory testing

These tests involve saturating the cartridge for which you wish to know the saturation level until it reaches its breakthrough point. To date, this is the most accurate method for prevention officers to measure the saturation rate. Unfortunately, this can only be done after use (and therefore after the possible risk has been taken), and remains expensive. It is therefore sometimes used to pre-dimension the prevention device or in the event of an incident. It is not used on a daily basis to ensure that operators are fully protected.

cartouche Honeywell RD40

The SatMETÆR, for measuring saturation in operating conditions.

This new device for the non-destructive measurement of gas filter saturation offers new prospects. Changes in the saturation of the gas filters can now be measured in operating conditions. The measurement is non-destructive (it does not affect the remaining potential of the gas filter) and works regardless of the pollutant.

SatMETӔR CleanSpace

Make sure that your respiratory protective equipment is fully operational and bring confidence to your employees

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