HVAC filters or air filters are one of the most critical and overlooked components of an HVAC unit. The simple-looking cardboard boxes are designed to filter the air. This is essential to protect the unit from suspended dust particles, fibers, hair, etc. Also, it improves the air quality coming out of the device by blocking bacteria, pollen, and other microparticles.

These are made of fiberglass or pleated paper and cardboard. Air filters must be replaced now and then to keep the device healthy. HVAC filters are categorized based on MERV (minimum efficiency reporting value) ratings.

• MERV 1-4: The cheapest of them all that block pollen, dust and carpet fibers, etc.
• MERV 5-8: These filters can trap mold spores, hair spray, and cement dust as well.
• MERV 9-12: These are quite effective and can trap particles as small as one micron, such as lead dust and auto emission.
• MERV 13-16: These supreme quality filers can trap the smallest of particles such as tobacco smoke, bacteria, and sneeze particles of up to 0.3 microns and larger.

Professionals advise regular clean-up of the HVAC device that includes changing the HVAC filters. It is essential to do so to keep the device free from dust and other harmful particles that get suspended in components and damage them. Regularly changing the filter prevents the device from dirt and debris and increases its lifespan.

Contrary to popular belief, air filters are mainly used to keep the device healthy than to improve air quality. These are primarily designed to prevent dust, pollen, microorganism, and other small particles from entering the device. In turn, the air coming out of the device is cleaner than it would be without the filter.

An air filter is essential even when the device is turned off as it keeps it safe from the suspended particles. The particles get trapped in the filter. Hence it is essential to change a filter before it becomes inefficient regularly.

The question arises, how often should one change HVAC filters?

It depends on the type of filter that you're using and dirt that surrounds a device. Depending on the thickness of the filter, you may be required to change it once in 3 months (1-2 inches) or six months (3-4 inches) or annually (5 inches). Usually, thinner filters need to be changed more frequently than thicker ones.

Choosing the ideal filter for your device proves to be more difficult than one can imagine. There are many things to consider while buying an HVAC filter from different materials and thicknesses to MERV ratings and prices. It is worth noting that not every filter is made for every HVAC device.

• Fiberglass filters: These filters are the least expensive ones and have the lowest MERV ratings. Typically lying in 1-4 MERV range, fiberglass filters are capable of trapping dust and carpet fiber.
• Disposable pleated filters: These filters have a MERV range of 5-7 and can trap smaller particles such as cement dust. These are made of a polyester material enclosed in a cardboard frame.
• Box and bag filters: These are a bit expensive but have high MERV ratings (8-15). These filters are capable of blocking particles that are smaller than even 1 micron in sizes such as lead dust and tobacco smoke.
• Hepa filter: These are the highest quality of filters with the best MERV, MPR, and FPR ratings. However, these might not be compatible with many of the HVAC devices. These HVAC filters do not come cheap.