Empty cylinders in prior service stored indoors must be considered as _____________ cylinders in determining the maximum quantities of LP-gas to be stored.

Empty cylinders that have been in prior service are treated as full cylinders for the purpose of determining the maximum quantities of LP-gas to be stored. The rationale for this is rooted in safety considerations. Although the cylinders might be empty to the user, they can still contain residual gas and must be treated as potentially hazardous.

When assessing how much LP-gas can be stored, it’s crucial to account for all cylinders that may still hold any amount of gas, however small. Treating these empty cylinders as full ensures that regulations regarding safe storage limits are followed, which helps prevent over-concentration of gas in any inspection area and minimizes the risk of incidents related to LP-gas exposure.

This highlights the importance of understanding the implications of previous use and safety protocols as outlined in NFPA 58, which aims to mitigate risks associated with liquefied petroleum gases.