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This article was originally published on July 11, 2022, and updated on April 23, 2025. In operations that involve a risk of fire or explosion, using the wrong pressure instruments can result in severe consequences, including operator injury, equipment damage or worse. To reduce the risk of anything catastrophic happening, pressure switches and other instruments used in these environments must adhere to strict class and division codes. During my extensive career in pressure and temperature measurement, my expertise in this area is a requirement. I write about it often to help others know what to look for when purchasing instruments for their hazardous location applications. Read this article to learn about the different class and division codes and which ones will apply to your specific needs. You will also be directed to additional resources designed to deepen your knowledge even further about pressure instruments and hazardous locations.

Pressure switches that are used for industrial applications involving any kind of liquid, such as water, oil or chemicals - or processes that have a risk of explosion - must meet specific standards. Choosing the wrong type of instrument for these challenging conditions can be dangerous for your operation and your people. As a territory manager for Ashcroft, customers often ask me to explain the difference between a NEMA 4/4X pressure switch and a NEMA 7/9. The short answer is that one classification is watertight (NEMA 4/4x) and one is explosion-proof (NEMA 7/9). But that response doesn't tell you what you need to know about these instruments before selecting the best switch for your specific needs. Read this article to learn the differences between these types of switches and how each is designed for a specific purpose. When you're done reading, you will have a clear understanding of the pressure switches, features and ratings to look for when choosing the best instrument for your application. You can also deepen your knowledge by clicking on any of the related links to additional resources.

If your job involves the risk of a fire or explosion due to an explosive element that is present, you work in a hazardous location. These environments require strict adherence to safety protocols and regulations to protect both personnel and equipment. Even a small incident in these environments could lead to costly downtime or worse. Ashcroft is a trusted brand of pressure and temperature instrumentation that can be found in countless hazardous locations across the globe. We have a tremendous amount of experience in developing products that are built to ensure smooth operations and the safety of your team. In this Understanding the Basics article, you will learn more about hazardous locations, the organizations and standards that govern them, code enforcing authorities, how to prevent explosions and more. Throughout the article, you will also find helpful links and additional resources where you can gain additional knowledge about products and best practices.