Summary of "Most HEPA Air Purifiers Are A SCAM (There's A Better Option)"
Product Reviewed
HEPA air purifiers vs. DIY MV13 filter-based air purifiers (CR boxes) and Clean Air Kits’ PC fan air purifiers.
Main Features & Concepts
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HEPA Air Purifiers: Marketed for 99.97% single-pass filtration efficiency, especially effective at capturing ultrafine particles (<0.1 microns) and particles larger or smaller than 3 microns.
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DIY CR Box Air Purifiers: Use MERV 13 HVAC filters (typically 4 filters + box fan). They have lower single-pass efficiency (~50-90% depending on particle size) but much higher airflow, resulting in a higher overall clean air delivery rate (CADR).
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Clean Air Delivery Rate (CADR): The critical metric reflecting how quickly clean air is supplied or pollutants removed from a space. CADR matters more than single-pass filter efficiency for overall air quality.
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Clean Air Kits: A commercial product line using PC fans (instead of box fans) with MERV 13 filters, designed to offer high CADR with lower noise and energy consumption than standard CR boxes or HEPA purifiers.
Key Findings & Comparisons
HEPA vs. MERV 13 Filters
- HEPA filters capture more particles per pass, but their airflow is limited due to restrictive filters and smaller fans.
- MERV 13 filters have lower capture efficiency per pass but compensate with much higher airflow, resulting in higher CADR.
- Studies show DIY CR boxes with MERV 13 filters outperform many commercial HEPA purifiers in CADR, cost efficiency, and energy use.
- HEPA units often do not report CADR or only report it at their highest (noisiest) fan speed, which can mislead consumers.
- Actual HEPA efficiency can be lower than the marketed 99.97% when operating at high fan speeds due to increased particle penetration.
Cost & Energy Efficiency
- DIY CR boxes are significantly cheaper upfront (~1/10th the cost of HEPA units per unit of air cleaned).
- Clean Air Kits’ PC fan purifiers use less energy and are quieter than both HEPA units and box fan CR boxes.
- Clean Air Kits’ models are about 10 dB quieter and use about one-third the power compared to equivalent HEPA purifiers.
Noise Levels
- Both HEPA and DIY CR box purifiers can be noisy, especially at high fan speeds.
- Clean Air Kits’ PC fan purifiers are quieter, making them more suitable for continuous use in living or working spaces.
Particle Size Efficiency
- Both HEPA and MERV filters show a dip in efficiency around 3 microns (most penetrating particle size).
- MERV 13 filters also capture ultrafine particles effectively, nearly matching HEPA performance for these sizes.
- CR boxes maintain high CADR across a range of particle sizes, including wildfire smoke and virus-sized particles.
Virus Protection
- Studies show CR boxes can reduce bioaerosols (virus particles) by over 97% in 30 minutes, comparable or better than HEPA units.
Additional Features
- Clean Air Kits’ “Exhaler” model offers near-field source control by pulling breath directly into the filter, reducing viral transmission risk.
- Automatic restart feature after power outages is a convenience advantage of Clean Air Kits.
Activated Carbon Filters
- HEPA units often include activated carbon filters for VOCs and odors.
- Carbon filters have limited effectiveness, become saturated, and do not remove particulate matter or airborne viruses.
- Ventilation is a better solution for VOCs and odors.
Pros & Cons
DIY CR Box (MERV 13 filters + box fan)
Pros: + High CADR, cost-effective, energy-efficient + Effective across particle sizes, including ultrafine and viral aerosols
Cons: - Can be noisy due to box fans - Aesthetic and build quality may vary - Requires DIY assembly and some technical knowledge
HEPA Air Purifiers
Pros: + High single-pass filtration efficiency (especially for ultrafine particles) + Often includes carbon filters for VOCs/odors (though effectiveness is questionable)
Cons: - Lower CADR due to limited airflow - Expensive upfront and costly filter replacements - Noisy at high speeds; CADR often reported only at max settings - May underperform in real-world conditions due to high face velocity
Clean Air Kits (PC fan + MERV 13 filters)
Pros: + High CADR with low noise and energy use + More aesthetically pleasing options available + Automatic restart after power outage + Comparable or better performance than DIY CR boxes and HEPA units
Cons: - Still limited carbon filter options (if any) - Not as widely known or available as mainstream HEPA brands
User Experience & Recommendations
- The reviewer experienced worsened allergy symptoms after switching from DIY CR boxes to commercial HEPA purifiers, which improved after reverting to DIY units.
- CADR is the most important metric for air purifier effectiveness, not just filter efficiency.
- For most home use cases, a DIY or Clean Air Kits style purifier with MERV 13 filters offers the best balance of cost, performance, noise, and energy efficiency.
- Sizing air purifiers by CADR relative to room size is critical; aiming for CADR at least two-thirds (or even twice) the room area in square feet is recommended for sensitive individuals.
- Multiple units can be used to cover larger spaces effectively.
- Activated carbon filters are not essential for particulate removal and may not justify the extra cost or maintenance.
Verdict / Overall Recommendation
DIY air purifiers using MERV 13 filters (CR boxes) or commercial units like Clean Air Kits with PC fans provide superior overall air cleaning performance compared to most commercial HEPA air purifiers.
They deliver higher clean air delivery rates, are more cost-effective, quieter, and more energy-efficient. HEPA purifiers, while excellent in single-pass filtration efficiency, often fall short in real-world air cleaning due to limited airflow and high noise at effective settings. Consumers should prioritize CADR and consider DIY or Clean Air Kits solutions over traditional HEPA units unless specific needs (like dust exclusion or certain VOC removal) require otherwise.
Additional Perspectives from Speakers
- Indoor Environmental Professional (IEP): Initially recommended HEPA for capturing fine particles.
- Wayne Westerman & Rob Wisman (Clean Air Kits): Explained the importance of CADR over single-pass efficiency and detailed the advantages of PC fan-based purifiers.
- Joey Fox (HVAC Engineer): Emphasized total air cleaned over single-pass efficiency and downplayed the practical value of carbon filters.
- Research Studies (Porto, SRI Krishna, Holder): Provided empirical data supporting DIY CR boxes outperforming commercial HEPA purifiers in CADR and cost-efficiency.
- Reviewer: Shared personal experience, skepticism, and final endorsement of DIY and Clean Air Kits solutions.
Summary: Most HEPA air purifiers are overhyped and underperform in practical use. DIY MERV 13 filter-based purifiers and innovative PC fan purifiers (Clean Air Kits) offer a better, more affordable, and quieter solution for effective indoor air cleaning.
Category
Product Review
