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BMS Controls FAQ

What Is A Sight Glass Used For In Hvac?

What Is A Sight Glass Used For In Hvac?

Are you curious about the inner workings of HVAC systems? Have you ever wondered what that glass panel on your unit is for? Look no further! In this blog post, we’ll be delving into the world of sight glasses and their crucial role in regulating and maintaining air conditioning and heating units. From identifying refrigerant leaks to monitoring fluid levels, a sight glass is an essential tool for any HVAC technician or homeowner. So grab a cup of coffee and let’s explore the fascinating world of sight glasses in HVAC systems!

What is a sight glass used for in HVAC?

A sight glass is used to measure the air flow through an HVAC unit. Air flow is measured in units of CFM (cubic feet per minute). A sight glass helps maintain accurate airflow by displaying the actual air flow level.

How to use a sight glass in HVAC

A sight glass is used to measure air flow in an HVAC system. The glass is inserted into the airstream and its height above the chamber gauge indicates the amount of air being delivered. Sight glasses can be calibrated depending on the type of furnace or air conditioning unit they are used with.

What are the benefits of using a sight glass in HVAC?

A sight glass is used to measure the humidity in a room. When the humidity levels are too low, the condensation on the inside of the windows will not evaporate and will cause the windows to fog up. A high humidity level can also cause mold and mildew to form. By measuring the humidity in a room, you can keep it within tolerances and avoid costly repairs or replacements.


A sight glass is a device used in HVAC installations to measure the air flow and temperature. By reading the color of the liquid inside the sight glass, technicians can determine how much air is being circulated and what the temperature is inside the system. Sight glasses are an essential part of ventilation systems and are often calibrated to maintain set operating parameters.