What safety measure should be included in gas-fired systems?

Including a carbon monoxide detector in gas-fired systems is essential for safety. Gas-fired appliances can produce carbon monoxide, a colorless and odorless gas that is harmful and potentially fatal when inhaled in significant amounts. A carbon monoxide detector serves as an early warning system, alerting occupants if dangerous levels of this gas are present in the environment. This preventive measure is crucial in residential or commercial settings where gas appliances are used, ensuring that any malfunction or improper venting that leads to carbon monoxide buildup is quickly identified, allowing for prompt actions to safeguard health and safety.

The other options, while important in various contexts, do not specifically target the unique hazards presented by gas-fired systems in the same way. For example, a pressure relief valve is vital for systems dealing with pressurized fluids, but it does not address the specific risks of toxic gas buildup. A fire suppression system, while crucial for fire safety, does not specifically mitigate the risks associated with carbon monoxide exposure. Lastly, a vapor barrier is related to moisture control rather than gas safety, making the carbon monoxide detector the most relevant and critical safety measure for gas-fired systems.