What tool is commonly used to measure gas pressure in gas lines?

A manometer is a device specifically designed to measure gas pressure in various applications, including gas lines. It operates by measuring the height of a column of liquid (typically water or mercury) that is influenced by the pressure of the gas being measured. This tool can provide accurate readings of low pressure, which is essential for maintaining safe and efficient operation in gas distribution systems.

In contrast, a thermometer measures temperature, a barometer measures atmospheric pressure (not specifically gas pressure in lines), and an altimeter is used to measure elevation based on atmospheric pressure. These other instruments do not provide the specific information needed to assess and manage gas pressure effectively in gas lines. Thus, the manometer is the appropriate choice for this context.