Choosing the right respiratory filter - how to select the best respiratory protection
There are many difficulties when choosing the right respiratory protection filter. In the following blog post, we look at the different types of particle, gas and combination filters and filter classes and explain if a specialist is required for the right choice.
In order to select the right respiratory protection filter, a risk analysis of the area of use must be realised in advance. When selecting respiratory protective equipment, it is important to analyse the concentration of hazardous substances in the air, the oxygen concentration of the surrounding atmosphere and a number of other factors. Filters and respirators must be analysed as a unit - only the right combination can guarantee safe respiratory protection.
Determining the filter type
The EN 14387 standard defines colour coding and code letters to identify the filter types and numbers to identify the respective protection classes. The above table provides an overview of the different filter types and the substance groups against which they can be used.
Determining the filter class
Gas filters are differentiated by their gas absorption capacity, among other factors. This is indicated by the filter class. With a higher filter class, the greater the absorption capacity for the respective pollutant. The filter class indicates the pollutant concentration up to which a gas filter can be used. For example, a class 2 filter with a medium absorption capacity can be used up to a pollutant concentration of 5,000 ml/m³.
The gas filter types A, B, E and K are categorised into three classes:
The occupational exposure limit value (OEL) defines the average concentration of a hazardous substance in the air over a certain period of time at which no damage to health is to be expected. This value is given in mg/m³ or ml/m³.
The protection levels of the various mask types have an affect on the maximum use concentration of a filter device (see table). Only the individual substances are subject to the limit value.
The concentration of a hazardous substance at the workplace is just one factor that must be analysed when choosing respiratory protection. The concentration of a hazardous substance at the place of use is also decisive with regard to the respiratory connection. The protection level of the respirator in use is relevant here.
For the corresponding filtering device in relation to an area of application, the stricter (lower) value of the maximum permissible pollutant concentration applies: the maximum use concentration calculated from the Workplace limit value and the protection level of the mask or the maximum use concentration according to the filter class.
Half face masks and quarter masks are no longer sufficient to protect users if the determined maximum concentration of a hazardous substance exceeds 30 times the occupational exposure limit value for this substance. In this case, full face masks are required. If the calculated maximum use concentration and the maximum use concentration according to the filter class are exceeded, a filtering device is not suitable for achieving the protection target.
How long can a respirator filter be used?
The filter class and the concentration of pollutants present in the area of use are the two main factors that influence the durability of a respirator filter. Numerous other factors also play an important role: humidity, ambient temperature and, last but not least, the wearer's breathing must be taken into account. Due to these various factors, it is difficult to give an estimated service life for the filter. Gas filters are generally designed for single use, even if they are only used for a short time. They must be disposed of properly after use.
For the selection of respiratory protection devices, you must follow the formulas of the DGUV Rules 112-190. However, these can only be applied when it is clear which hazardous substances are present at the workplace in which concentrations. In addition, factors such as explosion risk, oxygen content, and possibly occurring mixtures of substances must be taken into account. Therefore, it is advisable to always rely on the expertise of a professional when selecting respiratory protection.
As with all other hazardous substances, the employer may only authorise work with hazardous substances once a risk assessment has been carried out and the necessary safety precautions have been taken. This article is not a substitute for professional advice or a risk analysis.
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Further links: DGUV Rule 112-190 „Use of respiratory protective devices“
