Top 5 Things to Consider When Evaluating Air Purifiers

The RSF series line of ISO-Aire HEPA air purifiers.

Indoor air purification solutions have earned their place in the 2020 global pandemic spotlight and their importance to our health has never been more critical. So, when choosing an air purification system, take time to understand why commercial grade, and U.S.-made is a sound investment.

Portable HEPA air purifiers are a proven and effective way to help protect against COVID-19, other viruses, bacteria, contaminants, pollution, VOCs, mold, and allergens. This method of air purification is recommended by ASHRAE and the CDC as a COVID-19 mitigation strategy for improving indoor air quality. HEPA filtration helps reduce spread of germs via airborne transmission and lowers risk of exposure to indoor contaminants. There are key considerations to account for when deciding on an air purifier for your facility. The most important is ensuring the proper size of the purifier so that it is providing the needed CFM (cubic feet per minute) for the room size.

1.     CFM output and purifier size

When considering an air purifier for your commercial, residential, school or healthcare facility, first calculate the CFM needed to achieve the level of protection desired. The total cubic feet of the area you want to purify will impact this greatly. The larger the room, the more CFM required to achieve the desired number of air changes. Take the room square footage and multiply by the ceiling height, this will give you the total cubic feet of the space. Then divide the cubic feet by 60 (minutes in an hour) and that will give you the CFM you need to achieve 1 air change per hour. For 2 air changes you would need double that number, for 3 air changes you would need triple that CFM and so forth. For 1500 sq. ft. spaces, generally 500 CFM would provide 2 air changes per hour. In a 3,000 sq. ft. space, you would need 1,000 CFM, and a 6,000 sq. ft. space would require 2,000 CFM to achieve 2 air changes per hour.

ISO-Aire HEPA air purification at a Minn. government building.

2.     Air changes per hour

Establishing the number of air changes per hour will greatly impact the amount of protection. The more air changes per hour the higher the protection and vice versa. For example, ASHRAE and CDC recommend a minimum of 2 air changes per hour for schools through a portable HEPA filter (this is in addition to the existing system's air change requirements). As you filter the air in the room more frequently, you are allowing less  time for a pathogen or contaminant to remain in the space. For example, an airline industry average is to implement 3 to 6 air changes per hour. With 6 air changes per hour, you would have the air changed out in the space every ten minutes (divide 60 minutes by the number of air changes. Another factor when considering the number of air changes is the density of people in the space. If you have high risk people (i.e., elderly) or high density of people in the same space it is better to have a higher amount of air changes.

It is important to note that fan power and reach of the purified air is critical.  If the fan or purifier CFM output is too low, or if the unit doesn't have the fan power to properly move or distribute the clean air correctly, the air purifier will short cycle, or re-clean the already cleaned air rather than doing a complete clean of the room. This leads to a localized pocket near the air purifier of clean air rather than the whole room. This is common with inexpensive big box retailer brands that have a CFM output of 50-200 CFM.

3.     Additional purification technologies

Some commercial HEPA air purifiers offer layers of indoor air protection and come equipped with ozone-free bipolar ionization and/or UVC sterilization. These technologies don't replace a HEPA filter but add to the overall effectiveness of the unit in the space. The bipolar ionization helps treat the air before it is filtered by the HEPA and also reduces odors and VOCs. UVC sterilization damages the DNA or RNA of a germ (virus or bacteria) so that it cannot replicate thereby rendering it harmless (learn more about UVC here).

Bipolar Ionization

UVC Sterilization

It is key with both of these technologies to use brands that are ozone-free and integrated correctly. All ISO-Aire commercial-grade air purifiers use carefully chosen ozone-free technology and are engineered to provide an effective solution with each component integrated properly. ISO-Aire units come standard with HEPA filtration and can be equipped with optional ozone-free needlepoint bipolar ionization and/or UVC sterilization. Purchasing a unit with these additional purification technologies is recommended as the solution is then a multi-purification strategy and the technologies complement each other with their own set of strengths.

4.     What to look for in a HEPA filter

The type, size and amount of filter media in a HEPA filter is important as it determines how well it will capture particles and how long the filter will last. Choosing a HEPA filter with a rating of 99.99% at .3 microns or better will ensure capture of extremely small particles like viruses and bacteria. HEPA filters are actually more efficient below or above the .3 micron size but are tested/rated at the .3 micron size as that is the hardest size particle to capture.

Medical-grade HEPA Filter

Prefilters, such as a MERV7 or MERV8, can greatly extend the life of a HEPA. Their role is to capture larger size particles which will leave the HEPA to catch the smaller harder to catch particles rather than load up with large ones.

The more filter media a HEPA filter has, the more contaminants it can hold before restricting airflow and therefore last longer before servicing. Unfortunately, inexpensive air purifiers lower cost by using a low amount of filter media for their HEPA filters. They are still a HEPA but are able to hold far less amount of contaminants, resulting in reduced airflow output of the unit not long after being put into service and also requiring frequent air filter changes that causes for higher service costs over the life of the unit.

ISO-Aire™ commercial air purifiers use a high capacity, medical-grade HEPA filter with over 270 sq. ft. of media to provide a 2 to 3 year lifespan on the filter at a 24/7 continuous use before service is needed. Using a high-capacity HEPA along with a powerful fan allows for an ISO-Aire™ unit to provide a high output of clean air even when the HEPA filter nears the end of its life. This greatly reduces service cost and provides for maximum protection.

5.     Enclosure and Fan Design

Last but not least, consider the overall design. This relates to the construction, the type of fan and bearings used, how the unit discharges air, and the noise level.

• The type of enclosure, whether plastic or metal, will have an impact on durability of the unit. Metal units will outlast plastic. Enclosure design also impacts the noise output. Units with sound attenuation should be considered as these will be quieter.

• The type of fan and its lifespan have a large impact on the reliability, service life and noise level of a purifier. Long life, commercial grade, backward curve ECM variable speed fans with the ability to provide 1" or more of static pressure should be considered. These are efficient, powerful and quiet when applied properly. When properly sized, the fan doesn't have to spin as fast to provide the required output of air. Low-cost units typically use a cheap and undersized fan that has to have a high rpm to provide the needed amount of airflow with low quality bearings. This causes excess noise and results in a lower lifespan.

• The airflow strategy of an air purifier also matters. The ideal design pulls from the bottom of the unit to pull contaminated air out of the breathing zone while discharging clean air high. This prevents short cycling and proper distribution of the air throughout the space.

• Room design and facility needs differ which is why an adjustable, multi-direction grille helps to dial in the flow of clean air being discharged out of the unit and ensures even coverage and air distribution throughout the space.

Top Air Purifiers for Offices

An ISO-Aire commercia-grade air purifier pulls in contaminate air and “throws” clean air throughout the room.

All ISO-Aire™ units are made in the U.S.A with high-quality UL listed components. The design utilizes an efficient and high-powered fan that also provides industry leading low noise levels. Along with being built with durable 22 gauge steel, sound attenuated enclosures, a pull low discharge high air flow strategy and an adjustable multi-directional grille.

Top 5 things to consider when evaluating air purifiers.