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If you have ever been confused about the term negative pressure, you are not alone. One reason the concept is so confusing is that negative pressure is not really negative at all. It is actually positive pressure, but it is negative in relation to atmospheric pressure. Let me explain. Early in my career (while working for an Ashcroft distributor) I had a difficult time with the term ‘negative pressure’. The only thing that I knew about pressure was filling up a balloon, a ball or a tire. How could pressure be negative? It didn’t make sense! I asked anyone and everyone to explain but never received a satisfactory answer. Today, as a Territory Sales Manager for Ashcroft, a recognized leader in pressure and temperature instrumentation - and 16 years of experience under my belt - I now have a clear understanding of negative pressure, and I am in a position to share my insight. In this article, you will not only learn how to answer the question, "What is Negative Pressure?", you will also understand how it relates to other types of pressure. At the end of the article, you will also see links to additional resources that may be beneficial to you.

This article was originally published on December 13, 2021, and was updated on February 4, 2024. Different industrial applications require different types of gauges to measure pressure at various points of the process. Mechanical pressure gauges, for example, can be used to measure absolute pressure, vacuum pressure and compound pressure. If you’re not selecting the appropriate kind of pressure to be measured, your gauge may not provide you with the required “readable” pressure scale. Ashcroft has been manufacturing pressure and temperature instrumentation since 1852 and as the senior product manager for process gauges, I have been fielding questions on the subject for the past 15 years. In this article, I will take you through the various types of pressure and review the different gauges and transducers available to meet your specific pressure needs.