What must be installed when a supplementary gas for standby use is connected downstream where a meter is not provided?

When a supplementary gas for standby use is connected downstream in a system where no meter is provided, it is critical to install equipment to prevent backflow. This is necessary to ensure that the supply of gas remains safe and uncontaminated. Backflow can occur if there is a pressure change in the system, which could lead to the gas flowing back into the supply line, potentially mixing different types of gases or introducing impurities into the gas supply. Therefore, incorporating backflow prevention mechanisms protects the integrity of the gas supply and ensures compliance with safety standards outlined in the National Fuel Gas Code.

In scenarios where an operating gas system is connected with standby or supplementary gas sources, backflow prevention is particularly important to maintain careful control over gas quality and pressure, further aiding in preventing any hazardous situations that might arise from unintended gas mixtures or pressure changes that could disturb the normal operation of gas appliances.