- Simple mechanical air cleaning (using physical filtration without ionizers, UV light, etc.), ideally because the unit has no potentially-harmful electronic cleaning features and not simply because those can be disabled
- Maximize Clean Air Delivery Rate (CADR) at ≤45 dBA sound pressure (noise level @ ~1 meter) so as to avoid provoking the filter getting turned off
- “Schedulable” and/or compatible with a plug-based timer or motion sensor to maximize filter life and minimize power usage and burden on people (ideally, it resumes its previous settings after power loss)
- Clean air discharging “upwards” to breathing height rather than side discharge (per Harvard Healthy Buildings study and ASHRAE 241), especially if a “45-degree” angle from vertical is used to promote better room mixing
- Suitability for a 900 sq ft (8500 cu ft) classroom, such as size, sturdiness, filter guards, fan blade finger protection, stability (against tipping over), and ability to impede turning down the fan speed
- A vacuumable or washable pre-filter can extend the life of the HEPA or high-MERV filter and is therefore a positive, especially if it can be accessed easily and quickly; activated carbon filters help with odors and VOCs (at the expense of CADR), but as they do not remove particulate matter or viruses, they are considered optional
- Confidence in the manufacturer, biasing toward those most likely to continue producing replacement filters (or for which reputable HVAC-standard or third-party options are available), and those offering longer and more comprehensive warranties that aren’t invalidated by classroom use
<aside>
↩️
Back to the Safe Indoor Air Resources homepage at safeindoorair.org.
</aside>