It depends on what level of filtration you are trying to achieve. Filters are used to clean air in a variety of applications. They work to protect people in public buildings, patients in hospitals, and critical manufacturing processes. Filters are carefully engineered and designed to operate at specified efficiencies. Higher filter efficiency means that a filter is retaining smaller particles. It is important to know why a filter is being used and what requirements need to be met (for example, efficiency, airflow, pressure drop, and dimensions) to optimize filter performance. If you are unsure, we would be glad to help you in your decision. You may contact us at +1 (414) 353-5800 or email us.

Airsan Corporation designs and manufactures permanent air filters for industrial and HVAC use. Airsan has been in business for more than 80 years and is known for the custom design and engineering of filters for customer applications.

Metal washable filters should be washed at least once per month and should last at least 5 years, if not more if proper servicing is performed. Servicing of the washable filter is fairly simple. To learn more, see “AIRSAN Metal Filter Cleaning Instructions.

All permanent metal air filters, regardless of manufacturer, must have an adhesive applied after cleaning. This is what truly makes the metal air filters effective. The adhesive acts as a tackifier, and when particles travel through the filter, they will stick to the adhesive. Airsan Film-Cor recharging adhesive is nearly odorless, has a high flash point and rapid wetting characteristics. A red dye tracer in the adhesive allows visibility of coverage. More Film-Cor information.

There are two methods to determine when your filter needs to be changed:

Visual Inspections – By looking at the filter and how “dirty” it looks can help you determine if the filter needs to be changed or cleaned.

Measuring Pressure Drop – Most fan/motor assemblies have a pressure drop rating. Having the ability to measure this pressure drop will help you better determine when servicing or changing is required.

Airsan can basically make your filter to any size requirement. If your requirement is too large for a single filter, then creating a filter bank is your best option. Filter banks are made up of multiple filters that are put into mountable retaining frames. Please see the Airsan Type AH Filter Retainer for more information.

Specifying air filters with the lowest possible pressure drop nearly always pays for itself. Generally, pressure drop is a direct function of the filtration efficiency; in other words, high-efficiency filtration results in a high pressure drop. Simply stated, pressure drop or static pressure is the amount of resistance as measured in inches of water (w.g.), which is produced when air is moved through an air filter, an air duct or any device that can impede air flow and cause resistance.

Think of pressure drop or static pressure as resistance. Imagine walking along on a level surface, at a normal pace. Minimal energy is used to keep walking. Now, let’s tie a line around your waist and put a 10-lb. weight at the end of the line. To maintain the same pace you may have to use a little more energy. Let’s assume each 10 lbs. is equal to 0.1″ of static pressure or resistance. Now let’s add another 10 lbs. for a total of 20 lbs. of weight or 0.2″ of resistance. It takes a little more energy to maintain the same pace. As we add more weight it becomes more challenging to pull the added weight and maintain the same pace. If we add enough weight you won’t be able to maintain the same pace and you’ll eventually slow down or even stop.

The only other way to keep moving is to add another person. This is how static pressure affects a fan/motor assembly that moves air in an HVAC system or any air-moving device. As static pressure increases, the horsepower of the fan motor is being used up. At some point, the static pressure will be higher than the motor can handle to maintain the same airflow, and it will slow down (back down) or even stop unless more horsepower is added to the motor.

You should know that most heating/cooling systems in residential and light commercial markets are designed to move 900 CFM to 2000 CFM at a total system static pressure of approximately 0.5″ to 0.7″ total pressure drop, including the resistance through the ductwork and the filter. So, if you put a filter with a higher resistance in the unit than the motor’s horsepower can handle, you will slow down the heating/cooling blower/motor and reduce the overall effectiveness of the system. This is why all filters that come with heating/cooling systems as original equipment are the least efficient, low-resistance filters.