Frequently Asked Questions

Everything you need to know about air purification, HEPA filters, CADR, ACH, and indoor air quality.

General Air Purification

What is ACH and why does it matter?
ACH (Air Changes per Hour) measures how many times your room's air volume is filtered per hour. The CDC recommends 5-12 ACH for effective reduction of smoke, allergens, and airborne pathogens. Healthcare settings often target 6+ ACH for optimal air quality.
Are DIY air purifiers as effective as commercial units?
Yes, when using quality HEPA or MERV13/14 filters. DIY builds with H13 HEPA filters achieve the same 99.97% particle capture as commercial units. MERV13/14 filters capture 77-88% per pass but achieve high effectiveness through multiple air changes per hour, often at 1/3 the cost of commercial units.
How often should I replace HEPA filters?
Typically every 6-12 months depending on usage and air quality. Monitor filter condition visually - replace when visibly dirty or when airflow noticeably decreases. Pre-filters should be changed monthly to extend main filter life.
Can air purifiers remove viruses?
HEPA and MERV13/14 filters can capture virus-containing respiratory droplets and aerosols. MERV13 captures at least 77% per pass, MERV14 captures 88%, and multiple air changes achieve high overall effectiveness. However, air purification is one layer of protection alongside vaccination, hygiene, and medical care. It's not a medical treatment.
How loud are DIY air purifiers?
Quality builds run at 35-44 dB, comparable to a library or quiet office - much quieter than conversation. This is achieved through efficient CPU fans and optimal fan-to-filter ratios. Traditional box fan CR cubes are louder at 52-55 dB on low speed.
Will an air purifier help with wildfire smoke?
Yes! HEPA and MERV13/14 filters are highly effective at removing smoke particles including dangerous PM2.5. For smoke odours, consider adding activated carbon filters. Achieving 5+ ACH can significantly improve indoor air quality during wildfire events.
How do I calculate the right CADR for my room?
Use our free ACH calculator! Generally, multiply your room volume (m³) by your target ACH (5-12) and divide by 60 to get required CADR in m³/h. For example, a 50m³ room targeting 6 ACH needs 300 m³/h CADR (50 × 6 ÷ 60 = 5 m³/min = 300 m³/h).

Product & Technology

What is a Corsi-Rosenthal (CR) Cube?
It's a simple air cleaner pairing powerful fans with relatively high flow MERV13/14 furnace filters that catch viruses and pathogens with 72-90% efficiency per pass. The CDC discusses them in its new 5 Air Changes per Hour minimum ventilation guidelines for indoor spaces. These DIY air purifiers are highly effective for removing smoke, allergens, and airborne pathogens.
How do Clean Air Kits compare with DIY box fan CR cubes?
Both use MERV13 or MERV14 furnace filters that capture at least 77% or 88%, respectively, of virus (and PM2.5) per pass. Depending on fan model and filter brand, Corsi-Rosenthal cubes with 4 filters on low speed have a clean air delivery rate (CADR) in the 300-450 CADR range using ~65W @52-55 dB. High-quality Clean Air Kits can cover this range using 10-16W power @42-44 dB, making them much quieter and more energy efficient.
How can Clean Air Kits be safer than HEPAs of comparable maximum capacity?
What matters for room cleaning is the total rate of contaminant particle capture. Many HEPAs run quietly at speeds much slower than their maximum rated capacity. The 'quiet' speeds tend to clean air less than half as fast as the HEPA's max rated capacity. A properly designed Clean Air Kit runs quietly at one speed - its full CADR capacity - providing a consistently high level of protection without excessive noise.

Testing & Certification

How were your CADR (Clean Air Delivery Rates) measured?
Clean Air Kits have been tested by Intertek for AHAM AC-1 CADR, AC-2 Noise & Power. ASHRAE 241 specifies reducing these to a single infectious aerosol CADR via the formula: VirusCADR = 0.3*SMOKE + 0.3*DUST + 0.4*POLLEN. Studies of exhaled viral aerosols show a particulate distribution closest to AHAM DUST. For optimal fan to filter-area ratios (1 fan per 1 sq ft of Filtrete 1900), results can be extrapolated amongst related models.
Have CleanAirKits been UL & FCC tested and certified?
Assembled units with CoolerMaster fans have been FCC & UL507 certified for US and Canada by Nemko Labs. Fully assembled units receive FCC & UL507 electrical safety marks. Due to factory inspection requirements, unassembled STEM kits don't receive the UL507 sticker, though they contain the same UL-registered components and assembly procedures as factory assembled units.

Operation & Features

Can Clean Air Kits run off a portable battery?
Yes! You need a USB C PD 12V DC barrel adapter with compatible PowerBanks. Options like the VRURC T2046 20000mAh or Charmast C2046S 20000mAh can power units for approximately 12 hours. With the USB PD cable, you can even run them off your laptop! Ensure you select the correct cables and power banks, as many only deliver 5V which leaves fans weak.
Which models have handles?
Most portable models include handles for easy transport between rooms. This makes them far more convenient than traditional box fan builds that require dolly straps. Check specific product details for handle availability.
Which models have mesh filter guards available?
Mesh filter guards are available for many models to protect filters from curious fingers and pets. While tens of thousands of CR Boxes have been safely deployed with exposed filters, guards provide extra protection. Remember to wear rubber gloves and an N95 respirator during filter changes, as filters accumulate dirt and pathogens.
Is there a fan speed control?
Most kits are designed to run at optimal quiet speed and don't include speed controls. They're already so quiet and energy efficient that speed control isn't necessary. However, you can easily add external speed control via a variable-speed 3-12V DC 2A power supply (must not exceed 12V, requires standard DC 5.5x2.1mm barrel connector).
Is there a timer or motion sensor feature?
Not built-in, but we recommend plugging through a timer, motion sensor, or light sensor so filters run when people are expected to be around. Many accessories are available online. Our purifiers are so energy efficient they won't use much energy overnight either - a typical unit uses about the same power as an LED light bulb (10-16W).

Performance & Efficiency

Does cleaning and sanitizing the air use too much energy?
No! Thanks to the efficiency of CPU fans paired with MERV13 filters, these purifiers use several times less power than most HEPAs. A Tower of Power can add 3 air changes per hour to a large classroom using only 16W of power - about the same as an LED light bulb. Energy efficient building retrofits are a vital tool against CO2 emissions, as positive for building efficiency as LED lighting.
Does a Clean Air Kit mix a room as well as a HEPA or CR Box fan?
Yes, depending on which fans you choose and their orientation. Fans with focused flow can be felt several metres away and help circulate larger rooms effectively. The throw distance is about the same as a CR Box fan on low. Experiments have verified that one properly sized unit can effectively remove particulates from a whole classroom or large living space.
Do they create a cold breeze during winter?
Airflow is gentle and focused. Units can be positioned to avoid direct drafts while still effectively mixing and cleaning room air. The air movement is comparable to a quiet office environment rather than a noticeable breeze.

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