--- title: HVAC Filter Status and Air Flow description: hvac air flow diagram filter status | hvac air filter status monitor sensor | mass air flow sensor | mass air flow sensor cleaner image: https://www.setra.com/hubfs/Air%20DP%20Filter%20Status.png --- hvac air flow diagram filter status | hvac air filter status monitor sensor mass air flow sensor cleaner | mass air flow sensor symptoms ** ** ** - Website Pages - Products [![Setra Systems Logo](https://www.setra.com/hubfs/setra-logo.svg "Setra Systems Logo")](https://www.setra.com/) ![drop-down-pressure](https://www.setra.com/hs-fs/hubfs/angle-arrow-pointing-to-right.png?width=15&name=angle-arrow-pointing-to-right.png) **[Pressure Sensors](https://www.setra.com/product/pressure)** [Differential Pressure Sensors](https://www.setra.com/product/pressure/differential) [Absolute Pressure Sensors](https://www.setra.com/product/pressure/absolute) [Barometric Pressure Sensors](https://www.setra.com/product/pressure/barometric) [Compound 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Differential pressure transducers are an integral component of measuring and monitoring both filter status and air flow in HVAC systems, both of which are more crucial than ever. ## Filter Status Filter status has become an increasingly important focus for [HVAC systems](https://www.setra.com/blog/hvac-applications-for-pressure-transducers) throughout the pandemic. Higher MERV rating requirements mean filters are more costly as well as change the efficiency profile of systems. A filter collects contaminants in the air, and this increases the differential pressure between the inlet and discharge sides. Changes to the differential pressure across a filter are measured by a differential pressure transducer and send a corresponding signal back to the building automation system. This differential pressure signal indicates the cleanliness of the filter; the higher the differential pressure the dirtier the filter is getting. Differential pressure transducers providing filter status can help prevent damage to the system and allow someone managing the facility to know when the right time to change the filter. This will help keep the building occupants safe, while not throwing money down the drain replacing a filter too early. To use a [differential pressure transducer](https://www.setra.com/product/pressure/differential?hsLang=en) to look at the status of a filter, you must install the transducer such that, the high port measures the inlet side of the filter and the low port will measure the discharge side of the filter. When the filter is clean the “Initial Pressure Drop” rating should be the only differential pressure that the transducer is measuring. The “Final Pressure Drop” is the rating the filter manufacturer has tested when the filter should be changed out due to particles and contaminants being trapped in the filter. Every manufacturer and system is different, so before setting those thresholds, please consult the filter manufacturer and system designer for guidelines. Differential pressure transducers are a cost effective and accurate way to measure and help maintain an HVAC system. ![Air DP Filter Status](https://www.setra.com/hs-fs/hubfs/Air%20DP%20Filter%20Status.png?width=1320&name=Air%20DP%20Filter%20Status.png) ## Air Flow Air flow and air changes per hour are another focus for current HVAC systems. With recommendations to increase air change rates & fresh air intake to reduce risks of spreading COVID-19, accurate air flow measurement is a key factor for controlling a safe environment. Since flow rate is an exponential equation, a highly accurate [differential pressure transducer](https://www.setra.com/product/pressure/differential?hsLang=en) is a cost-effective way to measure flow within a system or Air Flow Station. The higher the accuracy of the transducer the more efficient a system can be; letting the building controls ramp up & ramp down flow based on the true requirements instead of a wider error band in the transducer. 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