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Use a 12 volt blower fan with at least 150 pascal static pressure

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 with Intersurgical Hydromax HMEF) . However, this fan is now sold out.

San-Ace 109BC12GC7-1 is good alternative if user needs higher flow (33 L/min, 60 dBA against HMEF)

Sunon MF50151VX-B00U-A99 is also good fan for BunnyPAPR. (33 LPM , 63 dBA) Same flow as San-Ace, slightly louder, but lower cost. Delta BFB0512HHA-CZMQ is lower flow, quieter (20 L/min 55 dBA under HMEF resistance). This fan is ideal for <80 kg users. Its mounting holes must be enlarged for 3 mm bolts. I have worn this in OR for 11 continuous hours. Steady state EtCO2 was 40 with this fan and Intersurgical Hydroguard Mini.

Some fans have correct looking specs but falter during testing. For instance, Mechatronix B5015E12B-BSR achieved only 22 LPM but was a loud 65 dBA.

If you try other fan model, always verify flow rate against your HMEF's resistance is 20 to 40 L/min and pressure is at least 20 pascal. Larger users will need 30 L/min. Check EtCO2 levels via gas sampling for at least 20 minutes to verify steady state value < 42 mm Hg..

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