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Changes to Step #29

Edit by Guy Kuo

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[title] Fans Tested
[* black] Use a 12 volt blower fan because tubaxial fans usually lack sufficient flow against resistance. We are drawing air in ''through'' a viral filter. Going by just factory spec can be misleading. Those are for static pressure (zero flow) and free air max CFM (zero resistance). We must measure flow rate against HMEF flow resistance.
[* black] My original recommended NMB Technlogies BM5115-04W-B50-L00 blower fan static pressure of 0.803 in H2O (200.0 Pa) provided ample airflow (30 L/min at 64 dBA noise) . However, this fan is now sold out.
[* black] San-Ace 109BC12GC7-1 https://www.digikey.com/product-detail/en/sanyo-denki-america-inc/109BC12GC7-1/1688-1035-ND/6191751 is good alternative if user needs higher flow (33 L/min, 60 dBA against HMEF)
[* black] http://d.digikey.com/HS000xU3ppttIK40NAX00T7 Delta BFB0512HHA-CZMQ has also tested well. It is lower flow but muchflow, quieter (20 L/min 55 dBA under HMEF resistance). This fan is suitable for smaller users. Its mounting holes must be enlarged to fitfor 3 mm bolts. I have worn this in OR for 11 hours straight. EtCO2 at steadycontinuous hours. Steady state EtCO2 was 40 with this Delta fan and Intersurgical Hydroguard Mini.
[* black] http://d.digikey.com/HS000xU3ppttIK40NAX00T7 Delta BFB0512HHA-CZMQ has also tested well. It is lower flow but muchflow, quieter (20 L/min 55 dBA under HMEF resistance). This fan is suitable for smaller users. Its mounting holes must be enlarged to fitfor 3 mm bolts. I have worn this in OR for 11 hours straight. EtCO2 at steadycontinuous hours. Steady state EtCO2 was 40 with this Delta fan and Intersurgical Hydroguard Mini.
[* icon_caution] PLEASE DO NOT HORDE FANS. Only obtain the number you will actually ''deploy'' to providers. Hording deprives others in need during this COVID-19 crisis.
[* black] Other blower fans may yield more ideal combination of power draw, static pressure, flow rate, noise, and availability. 200 to 250 Pascale static pressure capability is likely best range.
[* blackicon_caution] If you change fan model, always verify flow rate against your HMEF's resistance is 20 to 35 L/min. Check EtCO2 levels via gas sampling for at least 20 minutes to verify steady state value < 42 mm Hg..
[* icon_note] Flows cited above are against a Intersurgical hydrogaurd mini. That HMEF has a spec flow resistance of 2.9 cm H2O at 60 LPM
[* blackicon_caution] If you change fan model, always verify flow rate against your HMEF's resistance is 20 to 35 L/min. Check EtCO2 levels via gas sampling for at least 20 minutes to verify steady state value < 42 mm Hg..
[* icon_note] Flows cited above are against a Intersurgical hydrogaurd mini. That HMEF has a spec flow resistance of 2.9 cm H2O at 60 LPM

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