We think we have all heard the word “HEPA” before, and it is usually associated with clean air. While in simple terms that is correct, we will be going into a bit more detail of what HEPA’s are, why they should be used in certain situations, and what you should be looking for.
Without getting too much into the science of things, HEPA is an acronym for high efficiency particulate air. Whenever you see the term HEPA being used it means that the filter has been made and certified in accordance with current HEPA filter standards. Nowadays you can find HEPA filters in household appliances such as fans and even vacuum cleaners.
But when it comes to property restoration we are not talking about household appliances containing HEPA filters, instead, we are talking about professional air filtration devices known as AFD’s. You may also hear other terms for them such as air scrubbers, negative air machines, HEPA units, etc., these are all terms used to reference an AFD.
When and why should you use an AFD?
In the property restoration industry AFD’s are mostly used in work sites (your home) that have suffered a contaminated water damage loss (category-3), fire and smoke damage, mould and asbestos remediations to name a few.
To put it simply AFD’s are used in situations where there are or is a chance of contaminants or high levels of dust present within an environment. They are used to help control and maintain appropriate air quality levels within your home, while also aiding in the elimination of odours.
The reason AFD units are so useful is because they offer multi filter protection in order to safely remove contaminants and particles from the air.
Typically speaking an AFD will have the following filters:
- Pre Filter Stage – this is the first line of defence, it is designed to catch the larger particles that are floating around, it helps prevent the valuable HEPA filter from jamming up with these larger particles.
The AFD unit will also have the option of using different kinds of pre filters depending on the application, including carbon filters which are designed to capture and absorb organic vapours. These are great help when dealing with smoke and fire damage jobs as well as category-3 water losses.
- Main Filter – this slot is reserved for the HEPA filter which is able to capture particles as small as 0.3 microns in size. To put it in simple terms it captures all the particles that cant be seen with the naked eye, and for comparison; the thickness of a human hair is about 40-50 microns.
So now we can talk about the specs of these AFD machines and why house-hold type HEPA machines (the ones you can buy at Walmart etc) are not up to snuff in a property restoration application. The main reason is their CFM (cubic feet per minute) output is generally too low, which is basically the amount of air the machine pumps out per minute.
AFDs will have higher CFM outputs usually ranging from 500 to 1000+, but why should you care about CFMs? Because the proper amount of CFMs will allow the right number of air exchanges to happen.
An air exchange means that the air within an environment in this case lets say a room, is completely changed with new filtered air. So depending on the situation and severity of a project, the air may need to be exchanged 4 -10 times per hour, if not more, and to achieve this a high CFM output is required. This continuation of air exchanges is what allows for the filtration and cleaning of the air within your home.
Anyways, we don’t want to get too technical on this but in case you do here is the formula for calculating the CFM required to achieve the number of air exchanges you desire:
Cubic feet of the space you want to treat X Air exchanges you want per hour / 60 = CFM needed
Note: The air exchanges per hour is typically determined by the severity or nature of a restoration project. For basic applications 4-6 air exchanges per hour would be fine. If you are finding 4-6 is not enough then increase it as needed.
Some of the AFD’s which we use in my business and are manufactured for property restoration applications include:
A quick note on the CFMs required, in situations where lets say 1000 CFM or more is required,it is good practise to use several smaller CFM machines that add up to the 1000CFM than it is to use 1 machine with a rating of 1000CFM as you can distribute the machines throughout the work site and thus increasing your capture areas.
Ok, so that was a crash course of AFDs and HEPAs. As a closing note we want to mention that if you find yourself in a situation where air quality is a concern and you are trying to deal high CFM AFD’s on your own then you should definitely seek help or at least some advice from your local property restoration company. As this could indicate that the conditions in your home are poor and in need professional restoration services.