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→Ventilation
Ventilation rates can be expressed in several ways:
<pre>Cubic feet per minute (CFM) or litres per second (L/s) of outside air brought into the boat
CFM per person: CFM/p
CFM per unit floor area: CFM/ft2
Air changes per hour (ACH)</pre>
Standards for ventilation differ, and have varied over time subject to lobbying, energy efficiency doctrines and the emergence of sick building syndrome. A reasonable yardstick is somewhere in the range of 0.5-1.25 ACH or, more precisely, 1.0 ACH translating to around 1.66 CFM per 100 cubic feet of cabin volume. You can double check this to ensure at least 15 CFM/p.
Let’s work a complete example. Assume a salon of 1280 cubic feet. At 1.0 ACH this requires 21.3 CFM:
<pre>CFM = Volume * ACH/60 minutes</pre>
The corresponding vent area with a velocity of 2 ft/s is:
<pre>Vent Area = CFM/(Velocity * 60 seconds)
= 21.3/120
= 0.18 sq ft
= 25.6 sq in</pre>
Close enough.