Occasions where the filter admits defeat

1. Floating catkins

Since ancient times, people have written many works about willow and poplar trees. However, the floating fluff in spring is a disaster for filters, as it blocks any air filter attempting to intercept it.

In addition to willow catkins, there are also many other plant floating catkins. But those floating catkins are not as widespread as willow catkins, and their impact on filters is not as severe.

If there are many willows in the location of the factory, corresponding measures should be taken in the air conditioning design. For example, changing the height of the air inlet or adding a protective net to the air inlet. If the measures are not appropriate, the filter can only be changed frequently during the floating season.

2.Ice rain and freezing fog

The filter will treat fine rain as particulate matter and block it, causing water droplets to freeze on the filter material below zero degrees Celsius and quickly seal the filter. At this point, any filter will admit defeat. A filter made of fluffy material (most low efficiency filters) can last for a while, perhaps it can endure until noon when the temperature rises and pass through. When the filter material is dense filter paper, one hour is enough to clog the filter.

There's also something called ‘freezing fog.’ This is a smaller and lighter water droplet that forms ice crystals on the surface of objects below zero degrees Celsius. The filter may become clogged due to ice crystal attachment.

If the factory is set up in these two environments, an additional set of filters needs to be left as an emergency backup.

3. Continuous heavy fog.

The filter is not afraid of continuous rain, but it is afraid of continuous fog. Mist is a tiny water droplet that touches the filter and mixes with the accumulated dust on the filter material to form mud. If the filter material is very fluffy, the mud will enter the downwind end of the filter with the wind, and the filter can still function properly. If the filter material is dense, mud will stick the filter to death.

For filtration or dust removal devices with pulse back blowing cleaning function, if there is mud on the filter material, the cleaning function will fail. It's okay for a day or two, but if it lasts for several days, it will have a serious impact.

4. Hydrofluoric acid.

Hydrogen fluoride forms hydrofluoric acid with water. Hydrofluoric acid has a strong corrosive effect on glass. The filter material of the HEPA filter is fiberglass. But some factories may have hydrofluoric acid, which is the most feared by HEPA filters.

For example, in the manufacturing process of televisions and computer picture tubes, the glass cover of the picture tube needs to be cleaned with hydrofluoric acid, and the cleaning work needs to be carried out in a clean workshop equipped with HEPA filters. Although the concentration of hydrogen fluoride in the workshop air is controlled within a safe range that is harmless to human health, it is sufficient to damage HEPA filters.

When high-efficiency air filters have to come into contact with hydrogen fluoride, the final resistance of the filter is no longer the basis for judging its service life. The filter may have been damaged by hydrogen fluoride before reaching the final resistance. At this point, it is necessary to mandate the replacement cycle of the filter.

There is a new HEPA filter material - PTFE that is not afraid of hydrogen fluoride, but if applied to the above situations, high efficiency air filters are safe, but the operators and air conditioning systems in the workshop are dangerous.