NFPA-99 Practice Exam

Central supply systems using gas cylinders shall have what type of valve to prevent backflow and to permit service to the header?

1. Ball

2. Bypass

3. Check

4. Relief

The correct answer is: Check

The correct answer is a check valve. In central supply systems utilizing gas cylinders, a check valve is essential for preventing backflow of gases into the cylinders. This mechanism allows gases to flow in one direction only, thus protecting the integrity of the gas supply system and ensuring safety in operations. The importance of the check valve lies in its ability to maintain system pressure and prevent contamination from other sources that might flow back into the supply system. Additionally, while servicing the system, check valves allow for maintenance activities on the header without interrupting the gas supply. This ensures continuous operation and reliability of the medical gas system. Other types of valves play different roles. For instance, a ball valve is used generally for on/off control but does not provide backflow prevention. A bypass valve allows for alternate flow pathways, which is not specifically meant for backflow prevention. Relief valves, on the other hand, are primarily utilized to release excess pressure and do not address the backflow issue in the same way that check valves do. Thus, for the purpose of preventing backflow and permitting service to the header in gas cylinder systems, a check valve is the most suitable choice.