Gasketed air conditioner or heating filters, leaky air filters, washable air conditioning or heater air filters: This article explains and explain leaky air filters and the value of gasketed air filters, followed by comments on the effectiveness of washable air filters.
This website answers almost any question you might ask about air filters for heating or air conditioning systems.
We explain how an air conditioning service technician will diagnose certain common air conditioning system failures or defects. In these articles we are referring to filters installed on central air conditioning or central heating systems that move air through air handlers and duct systems.
Standalone or portable "air cleaners" or "air purifiers" are generally ineffective in buildings. We include photographs to assist readers in recognizing cooling system defects.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?
The page top photograph is of a low-MERV HVAC filter in an air handler.
A gasketed heating or air conditioning system air filter improves the filter effectiveness. The benefits of a high efficiency air filter material when used in an air handler and duct system are not fully realized if air bypasses the filter around its installation frame due to poor fit or poor installation.
The filter shown here is not a high quality gasket-type air filter. [Click to enlarge any image]
That's why some manufacturers emphasize the value of air-sealing gaskets on their products.
Simple observations made in the field will make for agreement with the manufacturers that filter bypass is an issue at some heating or air conditioning installations.
When changing an air filter at a return air inlet or at an air handler, when the old filter has been removed, take a look inside the return duct at the return register, or inside the return plenum at the air handler, to see just how much debris is passing the filter.
[The photograph above shows how a badly-fit HVAC air filter can not only leak bypass air into the blower compartment but also it can collapse right into the blower fan - this is a potential fire hazard!]
On an old heating or air conditioning system where filters have been ineffective, not properly installed, leaky, or not maintained and changed on schedule, we often find quite a bit of debris entering the air handler and duct system.
This is in fact so common that most HVAC installers and technicians consider dirty ducts to be "normal".
And they're quite correct: typical house dust that has collected inside of a duct system is not normally a toxic substance.
But
1) a high level of dust and debris inside of an air handler or duct system indicates that system filtration has not been effective,
2) the dust level indicates that the system has been delivering dust and debris to the occupants providing poorly-filtered air, and
3) there is an increased risk of mold in the
duct or air handler system if moisture enters the system from a leak or from air conditioning condensate mishandling.
Washable re-usable air filters are very appealing from a cost viewpoint. I would look for data to indicate whether or not the washable filter runs at a lower MERV or filtering efficiency.
In our cascaded filter proposal (discussed at this website) we included and continued to use a washable filter that came with the equipment since it was not reducing the airflow CFM, but we preceded it with other filters for different purposes.
The photograph at above left shows a typical washable metal air filter used in central air conditioning systems, and at above right is a washable foam air conditioning filter used in a portable room air conditioner. Other types of washable air filters are available as well.
At left we illustrate a plastic and nylon washable air filter used in both window air conditioners and in wall-mounted split system air conditioner units.
Unlike the foam type air filter shown above, these plastic and nylon air filters withstand repeated cleaning without disintegrating.
The efficiency of these filters increases as debris begins to settle on the filter surface, but eventually the improvement in air filtration efficiency is offset by reduced airflow - so clean the air filters in accordance with the cooling unit manufacturer's instructions - typically monthly during constant use.
A metallic air filter (shown ) is not very efficient (effective) at trapping airborne particles when it is clean, though efficiency improves as it gets dirty. Other pleated, fabric or paper air filters that are also washable are more efficient at trapping airborne debris.
Be sure to read AIRBORNE PARTICLE SIZE DEFINITIONS & TYPES for a description of the sizes and behaviors of some of the common particles that are an indoor air quality concern.
...
Continue reading at MISSING / LEAKY AIR FILTERS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see these
GASKETED AIR FILTERS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
Or see this
Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia
Or see
Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia
Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.
Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca
In addition to any citations in the article above, a full list is available on request.