Code Change Summary: Requirements for major repair garages have been completely reworked.

In order to align with NFPA 30A-2015 Code for Motor Fuel Dispensing Facilities and Repair Garages, the language in Section 511.3(D) has been completely rewritten with new language covering major repair garages where vehicles (using lighter than air gaseous Class I liquids) are repaired or stored. As well, a new Table was added that sums up the requirements. New Table 511.3(D) is a replica of the corresponding portion of Table 8.3.2 of NFPA 30A.

Many of the requirements in the new table are the same requirements previously found within the text of Article 511 in the 2014 NEC^®. Now, they are simply found in the format of a table instead.

Not all repair garages service or store vehicles that use special fuels. For those that do, there are several factors to be considered in order to ensure a safe environment.

Some flammable liquids such as liquid propane (LP) are heavier than air while others such as hydrogen or natural gas are lighter than air. Heavier than air fuels tend to congregate al the floor level of the repair garage where concentrations are at their greatest. Lighter than air fuels tend to congregate at the ceiling level of a repair garage. Wherever the fuel vapors congregate is where the risk of explosion is at its greatest. This code section is about vehicles that use fuels lighter than air.

See the new Table 511.3(D) to determine the Extent of Classified Locations for Major Repair Garages with Lighter-than-Air Fuel.