Red Seal Plumbing Practice Exam

All medical gas distribution systems must have a backup reserve supply installed to ensure a constant and reliable source of medical gas. Option A, a water trap, may be necessary in certain situations but it is not a requirement for all medical gas distribution systems. Option C, a dust filter, is not directly related to the functionality of the system and may not be needed in all cases. Option D, an oxygen sensor, is important for monitoring the levels of oxygen in the system but it is not a mandatory requirement for all medical gas distribution systems. Overall, the most important and necessary component for all systems is a backup reserve supply.