When talking with fleet operators about natural gas vehicles, one of the most common misperceptions is that modifying vehicle maintenance facilties to accommodate NGVs is extremely expensive.  While most existing facilities were designed for vehicles operating on traditional liquid fuels such as gasoline and diesel, generally these same facilities can be modified very cost effectively to provide for the safe maintenance of natural gas vehicles.  Here are some facts that must be considered.

Why Are the Safety Requirements Different for NGV Maintenance Facilities?

Liquid fuels, such as gasoline and diesel, pool on the ground when leaked or spilled.  The National Fire Protection Association (NFPA) defines the area from the floor to 18 inches above the floor in facilities where vehicles operating on these fuels as a Class 1 Division 2 Group D area.  In these facilities, ventilation air is introduced at a higher level and exhausted in the lower 18 inch area inside the facility.

Natural gas behaves exactly the opposite of liquid fuels. When leaked inside a maintenance facility, natural gas, being lighter than air, rises to the ceiling.  In facilities where NGVs are being maintained, NFPA defines the Class 1 Division 2 Group D area as the area extending from the ceiling DOWN 18 inches.  Therefore, the facilities must accommodate the unique characteristics of the fuel and air must be introduced lower and exhausted at the ceiling.

What Are the Most Common Modifications?

There are three primary areas of consideration when looking at NGV maintenance facilities: ventilation, heating systems and potential ignition sources.  Each of these must be considered when natural gas vehicles will be maintained in a facility.  There are relatively straightforward measures and equipment that can accommodate the safety requirements for ventilation, heating systems and potential sources of ignition.  The key is to be familar with the relevant NFPA codes. 

I’ve Heard that Necessary Modifications Cost in the Six Digit Figures.  Is That True?

As a general rule, no.  For instance, to ensure proper ventilation in an NGV maintenance facility, measures could include the installation of methane detectors, modifying the HVAC systems, adding a supplemental exhaust system or installing appropriate exhaust fan(s) over the NGV maintenance bays.  The costs of many of these measures are not prohibitive in any way and might even be considered minimal compared to the potential life-cycle cost savings of operating NGVs. 

Why Have NGV Maintenance Facilities Modification Costs Been Overestimated?

Many of the examples we have seen involve extreme engineering measures that have been designed into a modification project.  These measures, while effective, are not the industry standard and definitely go beyond the requirements found in NFPA’s codes. 

Fleet operators who manage fleets where natural gas vehicles are maintained “in house” definitely must evaluate their facilities against the codes for necessary modifications–but also should be aware that most of the time, relatively simple and extremely cost-effective measures can be used to ensure safety and meet code requirements.

For more details on NGV Maintenance Facilities Modification, click here to view our Technical Paper.