How does the filter work?
Choose the right filter
Choose the right mask
Substances can be distinguished into (dust) particles, gases and vapors. Gases and vapors move independently in the air. A (dust) particle is a collection of molecules in solid or liquid phase (dust or mist). The lungs and alveoli are affected by particles (dust). In gases and vapors, the dangerous substances can also penetrate through the lungs into the blood, brain and nerves. Read more about risks of substances and vapors.
Respiratory protection is divided into two types of filtering: that of gases and vapors and of dust particles. The operation of these filters differ from each other. Below you can read the differences.
Hoe werkt het filter?Filtering dust
Dust is filtered out using statically charged particles in a filter cloth. The dust particles that are sucked into the mask through breathing are attracted by and get stuck to those fibers. The clean, filtered air goes through the mask and is breathed in.
Filtering gases and fumes
Gases and fumes are filtered out using a different principle. A cassette that can be attached to the mask contains active carbon. The air being breathed in is sucked through that active carbon. The molecules of the hazardous fumes attach to the active carbon, after which clean air is breathed in.
There are various types of masks available; from small mouth covers to complete compressed air breathing systems. Depending on the risks involved, it is important to choose the right protection.
Protection factorsThe combination of mask and filter provides a certain protection. The concentration of dust outside the mask is divided by the concentration inside the mask. The ratio between those two indicates the protection factor. However, although that measurement may seem to be objective, there are different versions:
Nominal protection factors:
The (filter) mask is tested in a laboratory, where it is assumed that the breathing protection device is worn correctly and there is no leakage, so it is a theoretical value.
Assigned protection factor:
Certain government agencies assign more cautious indications. Because everyday practice is different from a simulated situation in a lab, the assigned protection factors are lower, making it a more realistic value. In the Netherlands, we use the Assigned Protection Factors from the United Kingdom: APF (UK).
To select a mask with the right protection factor, a calculation is necessary, in which the concentration of hazardous material is divided by the acceptable boundary value of that material*. The result is the minimum protection factor that the breathing protection device has to have to offer legal protection.
* The boundary values are listed in the Overview Substances of the SER (Socio-Economic Council).
Standards that apply to the masks.
|EN136||standard that applies to the full-face masks|
|EN140||standard that applies to the half- and quarter-face masks|
|EN143||standard that applies to the particle filters (protection against dust)|
|EN14387||standard that applies to gas filters and combination filters|
|EN148||standard that applies to face masks using screw-on filters (DIN-thread)|
How do you select the right filter?
Consists of an active carbon that absorbs organic gases and fumes. The carbon can be treated in different ways to collect the desired substance. The active carbon in the filter has so much room that many molecules can attach to it. If all the free slots in carbon are occupied, the filter is saturated and any other molecules will pass through the filter layer.
High temperatures affect the effectiveness of a filter. Because molecules are more mobile, they will pass through the filter more easily. A high humidity also has an influence, because water vapor will also attach to the filter, causing it to saturate more quickly.
On the basis of the hazardous substance involved, a type of filter has to be chosen. The different types are indicated with letters and colors, for example green – K for Ammonia and red – Hg for mercury vapor. If multiple substances are filtered, multiple letters and colors are displayed on the filter.
It is also possible to combine different filters. They are manufactured on a modular principle, so you can use as many filters as you like.
The gas filters have a capacity for a certain concentration of gases or fumes. The capacities are divided into three classes, which indicate the maximum capacity (and lifespan) of a filter. Note that they do not refer to the protection factor!
Class 1 – 0.1% / 1000 ppm
Class 2 – 0.5% / 5000 ppm
Class 3 – 1.0% / 10,000 ppm
When the filters are almost saturated, a harmless quantity is allowed through. Most wearers will smell or taste it. This is the most important signal that the filters have to be replaced. Needless to say, the employees need to be alert to the saturation. Make sure they are aware!
These consists of polypropylene fibers and catch dust particles and mist. Larger particles bump into the fibers. Smaller particles are deviated by the airflow and caught by the fibers. On average, large particles between 0.1 and 1.0 are the hardest to catch.
The qualities of the fibers determine the level of filtering. They are divided into three classes:
P1 – filters 80% and is suitable against irritating (particulate) matter
P2 – filters 94% and is suitable against hazardous particulate matter
P3 – filters 99.95% and is suitable against toxic particulate matter
The stronger the filter, the higher the breathing resistance (heavy breathing). So do not automatically select a higher protection level. The particulate filter will not start leaking because of saturation, but breathing will become more difficult when the filter gets polluted, which means that the filter needs to be replaced. Air being breathed out brings moisture to the filter, as a result of which particles will get stuck more quickly. To prevent that from happening, some masks provide an exhalation valve.
Combine the two filters discussed above.
How do you choose the right mask?
Because of the great diversity of substances, choosing the right protection is difficult, while making the wrong choice can have fatal consequences, which is why it is crucial to make a well-considered and correct decision.
These are the typical mouth masks you see in many work areas, covering the nose and mouth, preventing the substances from being breathed in. The air is cleaned by a standard filter. After the filters have become ‘saturated’ with hazardous substances, they have be discarded. These masks are the least comfortable, but also a lot cheaper than the rest.
Half-face masks cover a similar part of the face, but substance and gas filters can be attached to them. The advantage is that the filter (boxes) can be replaced, making the mask reusable again and again.
There are also half-face masks with standard integrated gas and particle filters available, so the filters cannot be replaced. These are especially suitable when working with the same known substances. The advantage is that you do not have to keep looking for the right filters and, because they are so compact, they are comfortable to work in and can be used underneath welding caps.
These are like half-face masks, but they also cover the eyes with a transparent plate. Because the protected area is larger, the mask provides a better fit and offer more protection (protection factor).
In spaces with a very high concentration of particles and fumes, motorized systems are the most effective. You wear a helmet that covers the entire head. On your back, you wear a filter with a motor unit. Via a tube, oxygen is blown into the helmet, which is brought to the mouth via the forehead. The oxygen is then removed via the bottom of the helmet, allowing you to breathe freely without breathing in the air your breath out again.
When using the masks listed above, you depend on the air around you. When is that too contaminated to be filtered, the air is brought in via a tube from a safe zone elsewhere. When the tube is longer than 9 meters, propulsion is necessary. In this document, we do not discuss independent breathing protection in detail.
The mask has to provide sufficient protection from risks. The filter provides some resistance, while oxygen will always choose the path of least resistance, which is why air will always leak from the sides of the mask.
However, the mask will have to provide enough protection to make sure concentration levels of the hazardous substance stay below boundary levels. In the Netherlands, we the Assigned Protection Factor of the United Kingdom (APF UK), a value that is included in the product description or even in the product name.
Certain masks cannot be combined with all filters, which is why you have first determine the protection factor and then examine possible combinations, which can be found in the EN529:200 standard.
Comfort is an important factor in safety. It determines people’s motivation to wear or not to wear protection, which is why you should try to select the most comfortable solution possible.
Heavy protection is also heavy to wear and makes people less mobile, which is often burdensome during heavy or prolonged activities. That is why, sometimes, choosing a light mask with a strong filter is a better solution.
On the other hand, using a strong filter makes breathing harder, which means people will get tired more quickly when doing heavy or prolonged work.
That is why manufacturers try to make heavier masks more comfortable, equipping them with rubber parts to offer a better fit to the face. Also, using broader straps distributes the weight more evenly across the head.
Many activities require multiple PPG, like ear muffs or welding caps. So select a mask that does not get in the way of the other PPG or try to combine them in a single PPG.
Of course, the masks also vary in price. Generally speaking, heavier masks are more expensive. However, depending on whether they can be reused, they may actually turn out to be cheaper. So look at how long you will use them: just the once for a construction job? For a complete shift in a factory? Or for visitors to the factory as well?
How do you make sure protection is worn correctly?After you make the right choice, you are not there yet. Safety depends on whether or not people use the PPG correctly. So make sure you provide proper instructions and create support for personal protection.
Of course, safety is more important than comfort. But when you increase protection, your employees may not appreciate the change. When you move from a half-face to a full-face mask, it is important to choose the most comfortable option. That way, you can create support among the people having to wear the mask.
Of course, each workplace has its own risk level. Nearer machines or electric lines, the risks are higher than they are elsewhere. When there is a risk that the people who are working in one area are using protection designed for another area, it may be best to use the same breathing protection everywhere. For instance, if a P2 filter is needed in work area A, and a P3 filter in work area B, there is a risk that someone will accidentally use the wrong filter. By deciding the use a P3 filter everywhere, you can eliminate that risk.
In that case, the less dangerous work area will be ‘overprotected’. Less comfortable, because a P3 filter has a higher breathing resistance. But it will be safer.
Now that the choice has been made, using the gear properly is also essential! Using a toolbox with a manufacturer or dealer can increase work safety. Predominantly because your employees are made aware of the dangers when not using the gear, or not using it correctly.
If you explain to your employees what the risks are when they ignore the explanation, you let them know what the risks are. As a result, they will listen, not because their ‘boss’ is telling them to, but because they want to.
The mask has to close around the face as seamlessly as possible. But since every face has a different shape, no mask will fit perfectly. Doing an (annual) fit test, you make sure that the mask will fit the face.
The test uses a harmless, yet very odorous substance, allowing the user to indicate how well the mask is working. In addition, there also a quantitative measurement using a fit testing device. However, that test may never be used as the official Assigned Protection Factor.
In the Netherlands, (at the moment) fit tests are only legally required in the asbestos sector. However, it is recommended with prolonged activities or when working with very hazardous material. After all: work safety is all about using the protective gear correctly. That is why it is a good idea to combine a fit test with a toolbox. You can come into contact with certified testers via the sector organization VVGW.
Maintenance is very important with regard to breathing protection. Often, it is a neglected area. Something many people forget. But, of course, to breathe in clean air, the mask also has to be clean.
Many masks can be taken apart and cleaned with a moist cloth. Some masks can even be put into a washing machine. In addition, some parts can be replaced to keep the breathing quality as high as possible. These instructions can also be explained in a toolbox.
The masks discussed above offer great protection. But it is efficient to take other measures as well. When the work environment contains high concentrations of hazardous substances, filters will quickly saturate. So, in addition to using PPG, also provide ventilation if that is possible, which prevents high breathing resistance and an unnecessary waste of filters.
AdviceCan't figure it out? Please call me for additional advice. It is important that you make a safe choice!
Marjorie - Operational PPE-adviser
+31 184 434 455 firstname.lastname@example.org