For this comparison, we used a popular brand large HEPA purifier that closely matches our Luggable XXL in CADR (410 cfm) and $300 price (same as XXL Kit plus a pair of Filtrete). This HEPA model was recently exposed as having more like E11 95% or H12 99.5% filtration efficiency than "true" HEPA H13 99.97%, but as we explain here, such marketing discrepancy can be a net good for performance in a room purifier.
Unsurprisingly, their noise specs are a bit of a stretch too, as their product page says 26-55dB. But 55dB is the 4th speed. It doesn't reach 410 CADR until the 5th "turbo" speed measuring 64 dB on the NIOSH app with our iPhone 1 meter away -- some reviewers have clocked it @68 dB! (Compare to 46 dB for the XXL). Some people may tolerate 55 dB but 64 dB substantially hinders conversations.
Turbo Speed Comparison
At that 5th Turbo speed this model has a strongly focused upward airflow for great throw and room circulation, seemingly stronger than the XXL. With matching 410 cfm CADR on Turbo it should clear the 600 sq ft apartment just like the Luggable XXL. For the most part it did, even down to air change rates matching 4 ACH for smallest .3um particles and rising to 5.5 ACH for larger particles.
(NOTE: this data collection was done on a different day than XXL with half the equilibrated outdoor pollution, but this should not impact exponential drawdown. SNR did get a bit dicey for 5 & 10 um particles with low counts on the TemTop).
We noticed the HEPA purifier produced a few minutes more lag for the ▼Far Corner, ◆ Kitchenette, and central 🔺Sofa locations on opposite side of the room. For instance, the HEPA takes 5 minutes to drop .3um particles at far ◆ Kitchenette in half but only 2 minutes for nearer locations. The XXL better synchronizes drawdown in these far flung locations, hugging the ACH reference decay line tightly in the least noisy .3-1um datasets. How could our SickleFlow fans be mixing the space better than this very well-focused HEPA with upward throw, when PC fan detractors expected the opposite?
Remember the XXL lowered particle counts most and first at the 🔺Sofa in the center of the room, 3.5 m in front of the XXL side fans? For the HEPA, this central 🔺Sofa location did not lead -- it lagged, while locations along the HEPA's wall led.
Our explanation? When XXL is placed along a wall with side fans facing center of the room, 4 SickleFlow fans send clean air toward the ceiling, and 5 SickleFlow send clean air directly to the center of the room. From 🔺room center, XXL cleaned air can spread to the far wall and corners a couple minutes faster than up-flow HEPAs! For the HEPA to mix the room more evenly, it would need to be placed at the center of the room, next to that sofa.
Noise-matched Medium Speed Comparison
What happens when we turn down this large 410 CADR HEPA to its middle speed, where its noise measures 48 dB, just a tad louder (and whiter) than the 46 dB XXL? Because the Intertek's AHAM AC-1 official CADR testing costs about $5k per model and speed, manufacturers only report CADR for one speed, their top speed, regardless of how loud that is. This leaves consumers flying blind as to the CADR and ACH they're getting at medium speeds where noise is more tolerable and sustainable.
For this popular model, the CADR drops roughly in half producing only 2 ACH at its 48dB medium speed. Two of these units operating at medium speed would be necessary to reach 4ACH for .3um particles (~SMOKE) and 5ACH for 1.0um particles (~DUST). We suggest a general scaling rule that HEPAs producing 60-70dB noise at their turbo speed can only be expected to reach half their advertised CADR and ACH when turned down to reasonable 40-50dB speeds.
Conclusions
Once again the results of this experiment were unexpected, and taught us something new about purifier placement. The Luggable XL and XXL side fans can mix a large room quite evenly with their back side against a wall projecting toward the center of the room. A traditional up-blowing HEPA of same capacity needs to be at room center for equitable mixing to all walls. A great engineering professor once told us after a counter-intuitive holography demo, "Intuition is what you build after doing experiments that disprove common sense!"
Secondly, if you're aiming to create quiet, even coverage of your house with fast drawdowns of infectious aerosols (i.e. high ACH), PC-fan Corsi Rosenthal boxes are double the value of even the most popular, economical large HEPAs. To get the same quiet cleaning rate as a Luggable XXL, two of these large HEPAs on medium are necessary. Or you could go with an even larger HEPA like Coway Airmega ProX or SmartAir Blast that cost 2-3x as much, but have much quieter ACTUAL top end noise than the economical HEPA tested here. The choice is up to you!
Our customers are sharing anecdotes of COVID infections avoided despite unknown infectious persons in their house or dorm room, and we've avoided pre-test spread from infected persons sleeping in our own well-covered bedrooms. Because airborne pathogens are always looking to spread through the path of least protection (least ventilated space), the best clean air strategies create consistent, even coverage of occupied household rooms, classrooms, vehicles and eating areas.
