Choosing an In-room HEPA Air Cleaner: Fixed or Portable?

As building facility managers make plans to welcome people back to schools, businesses and retail locations in the future, indoor air quality (IAQ) is a critical piece of any COVID-19 risk mitigation strategy. Ventilation and filtration efforts to deliver clean, healthy air are key to preventing the exposure and spread of airborne contagious diseases, like COVID-19.

While there isn’t a one-size-fits-all IAQ strategy for all buildings, experts agree that increasing the air change rates per hour (ACH) to between 3 (the bare minimum) to 6 (ideal) ACH is an important step toward keeping building occupants healthy during the pandemic.

There are two ways to boost ACH:

1. Increase air changes through outdoor ventilation. This happens either through a central mechanical system (an HVAC system) or naturally (via opening windows and doors); or
2. Increase air changes via recirculated air that is cleaned. This happens by filtering air centrally by the HVAC system or using in-room fixed or portable HEPA air cleaners.

What is an in-room air cleaner?

An in-room air cleaner is a device that is installed in a room or space independent of any HVAC system. In-room air cleaners pull air from the local environment, run the air through a series of filters, and send the air back into the space. In-room air cleaners may be fixed (e.g., mounted on the ceiling) or portable and may go by many different names including portable, local or standalone air cleaners or air purifiers, HEPA filter and recirculation units.

The good news is that building facility managers can quickly and cost effectively increase the air change rate in their buildings with an in-room air cleaner. What’s tricky, however, is that not all air cleaners are created equal.

Fixed vs. portable

There are two types of in-room air cleaners: fixed and portable. Choosing the right solution depends on whether you are looking for a long- or short-term fix for the problem and your budget parameters.

• Fixed units, which are mounted to the wall or ceiling, are more expensive to install, but are a permanent, long-term investment to not only help mitigate COVID-19 risks today, but also to help reduce the risk of airborne viruses in years to come. On top of that, fixed units are proven to deliver better performance and are often quieter than portable units.
• Portable units, which sit on the floor or any flat surface, are often more affordable up front because they involve no installation costs. Just plug the cord into the wall to operate. However, portable units are more temporary and harder to track, take up valuable floor space, are often lower powered and louder than fixed options, and present trip hazards from cords. Importantly, they may not be as effective if not placed centrally in a room or if they blow air across the breathing zone.

For organizations considering an in-room air cleaner for their building, we’ve put together a side-by-side comparison of both portable and fixed air cleaners.

Don’t forget to factor in background noise

One thing we hear time and again from businesses and schools we speak with is the importance of finding a quiet solution. If the in-room air cleaners are too loud at the optimal fan speed, there is a risk that people will turn the device down, turn them off, or use them infrequently, defeating the purpose of having in-room air cleaners.

If multiple in-room air cleaners are required for a larger space, then sound levels need to be added together to get the sound rating for the solution being considered. Building facility managers should look for the quietest options available while also considering performance in terms of ACH delivered.

The location where the air cleaner is placed in the space also has an impact on whether noise from the unit will be disruptive. The closer the air cleaner is located to people, the more disruptive the sound from the air cleaner will be. Imagine positioning the air cleaner in the center of a room — which happens to be the center of a conference room table. A benefit of fixed units over portable devices is that fixed units can be mounted to the ceiling or installed in a ceiling plenum with duct work and sound attenuation to deliver quiet, less disruptive air cleaning.

The bottom line

Comparing the two options, fixed in-room ceiling mounted HEPA air cleaners are typically quieter, more effective and work faster than portable HEPA filtration units as pointed out by industry experts:

“With respect to air cleaners for airborne pathogens, there is a very clear hierarchy of performance. At the top, we find ceiling-mounted filtration systems that allow for a very high level of control in specific areas because they are ducted and unobstructed by objects in a room. This is extremely important for issues like COVID-19, where aerosolized viruses can be removed at the source. The next level down is portable filters, which are 20-50% less effective than their counterparts mainly due to challenges with placement in a space. Last is traditional central filtration systems, which force virus particles to travel a long distance prior to being removed.”
– Raefer Wallis, Founder of RESET

“Because airflow patterns within a room affect the effectiveness of in-room air cleaners, fixed in-room air cleaning systems are preferable to portable ones, because they more reliably achieve adequate room air mixing and airflow patterns if installed properly.”
– Ontario Health Technology Assessment Series

For school administrators and facility managers, download this free guide to learn more about COVID-19 mitigation in the classroom.