AFS-953 combines the precise operation of our AFS series with convenient features for industrial and commercial air handling applications. The AFS-953 can monitor positive, negative, or differential pressure (flow) of air and noncombustible gases. It is ideal to monitor combustion air, furnace pressure, ventilating blower operation, inflatable structure pressure, fume hood operation, bag house air flow, dirt accumulation in air filters, and heat-transfer air flow. The most common specific application for the AFS-953 is as a Low Draft (Negative Pressure) Cutoff Safety Switch for combustion draft control systems where individual pre-purge is needed. The field–adjustable set point range is 0.05″wc to 12.0″wc with a 20-second pre-purge delay and an 8‑second (± 3 seconds) time delay relay sequenceThe time delay prevents nuisance shutdowns due to normal draft fluctuations. The AFS-953 is available in NEMA-1, NEMA-4, and NEMA-7/NEMA-9 enclosures.