Explaining Furnace Filters

Explaining Furnace Filters

As winter approaches, many homeowners and building managers start thinking about their furnace and whether it’s performing as it should. One key aspect of the way the furnace runs is whether it’s fitted with a suitable filter, and whether the filter has been changed recently.

A filter that’s doing its job well will be ensuring that the air in the building is healthy, and at the same time protecting the furnace from damage and expensive repair bills.

Different Kinds of Filter for Different Air Particles

The air is full of differently sized particles. For example lint, mould spores and pollen are comparatively “large”. In the world of furnace filters, large means between 6 and 100 microns (a micron is a millionth of a metre). Just for comparison, a hair from your head will be between 3 and 300 microns. Medium sized particles include animal dander, skin flakes, bacteria and dust. And then there are the nasty small particles which include viruses, smoke and smog.

Explaining Furnace Filters

Some filters only remove large particles – others remove small and medium ones too. To help homeowners and building supervisors select the filter they require, filter performance is graded according to a British Standard (BS) rating which is based on the size of the particles you need to trap. Filters are assigned letters to show their grading – F is for fine filtering, M for medium filtering and G for coarse filtering – that is, only larger particles will be trapped. Whatever the grade of your filter, if it has been tested to the BS EN 779:2012 standard, you know it will perform efficiently.

Furnace Filters to Improve Working and Living Environments

A properly working furnace filter will remove any particles that can adversely affect the lungs of people working or living in the space. At the same time, it will keep the furnace working properly. Dust tends to collect inside the coils, and some filters are washable or reusable. Some are sprayed with coatings to collect small particles. Other filters consist of a cellulose of fibre glass pad – these will filter larger particles.

More sophisticated filters may be made of pleated polyester which provides more effective filtering. The fibres can be statically charged so that they draw in small particles.

You can even get electronic filters in which air particles are given a positive charge which makes them attracted to a negatively charged element. These filters are more expensive and require more maintenance but they can remove small smoke particles, and for some users that is a deciding factor.

Explaining Furnace Filters

Your Pet May Shorten Your Filter’s Life

Furnace filters are great for removing allergens from the air, including animal hair and dander. However, the more work you make the filter do, the more often you need to replace it. So if you have several cats, for example, the filter will become clogged and ineffective more quickly.

Change Filters Regularly

It’s important to change the filter regularly because it loses efficiency over time. Some filters can be washed or hosed, others need to be changed completely. An efficient filter will reduce maintenance costs on the furnace because it will stop dust collecting inside it, so filter changes will pay for themselves.

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