Intersection gives approximate equivalent chill temperature that is, the temperature that would cause the same rate of cooling under calm conditions. It is the rate of relative air movement that counts and the cooling effect is the same whether you are moving through the air or it is blowing past you.
Danger is less if subject is active.
There is no substitute for it. The table serves only as a guide to the cooling effect of the wind on bare flesh when the person is first exposed. General body cooling and other factors affect the risk of freezing injury. Wind chill factor chart adapted by the Missouri Department of Health from Fort Leonard Wood Form 8-2264 dated June 1991.