For the needs of fire safety engineering calculations, the dynamic smoke detector
model presented here is reasonable. A first (and safe) approximation would be to use
a characteristic length of 10 m for point-type smoke detectors. If better accuracy is
needed, the parameters can be determined for each detector model by running a
sufficient series of wind tunnel tests at different flow velocities and rates of rise of
smoke density. The model is not, however, good for the detectors with advanced signal processing, because their response model may not be simplified as described
here