NFPA 99 specifies that the medical gas piping system shall be protected against all EXCEPT which of the following?

• A. Combustible liquids
• B. Physical damage
• C. Corrosion
• D. Freezing

Answer: (A)

NFPA 99 aims to keep medical gas piping reliable by guarding it against hazards that could directly compromise the system’s safety and integrity. The protections it specifies are against physical damage (to prevent punctures or deformation from bumps, impacts, or handling), against corrosion (to maintain material integrity and prevent leaks or contamination), and against freezing (to avoid brittle fractures or blockages in cold environments). Protection against combustible liquids is not a listed requirement for medical gas piping, because the standard focuses on the piping’s resilience to environmental and mechanical hazards within the healthcare setting, not exposure to flammable liquids. Therefore, combustible liquids are the exception.