... are designed for HVAC, detection of blocked filters, fan suction, air flow monitoring in ducts, pipes, tunnels, differential The AFS are ... switches designed for HVAC, detectionof blocked filters and fan suction, air flow monitoring in ducts, pipes, tunnels,and other energy anagement ... . It may be used to sense positive,negative or differential air pressure.Features:1) Field ajustable range: 0.05±0.02 ...