F5 fans portable ventilation fan by dl wholesale combines strength and quality into one, through the use of sturdy, durable steel and top-tier quality bearings. F5 portable ventilation fans feature advantages such as: powerful wind-flow, low heat output, energy efficiency, easy transportation, and a sturdy, protective guard for added safety. F5 fans are recommended for industrial use only. Cfm is an abbreviation for cubic feet per minute (cu ft/min).When used in the context of a particle counter's flow rate, it is a measurement of the velocity at which air flows into the sample probe. For example, a flow rate of 0.1 cfm means the particle counter will sample 0.1 cubic feet of air per minute. 8 portable ventilation axial fan.