Existing maintenance facilities designed to service con ventionally fueled (gasoline and diesel) vehicles are typi cally fitted with ventilation systems that capture vapors in the event of a spill. Because fuel vapors are heavier than air, the ventilation system pickup point is typically located near the floor of the facility (Figure 17) where the vapors will accumulate. A maintenance facility that ser vices both conventional and CNG vehicles needs ventila tion systems to address conventional fuel vapors as well as natural gas releases.
An existing facility that is modi fied to service CNG vehicles must retain the ventilation Space Heating Maintenance facilities in most locations require some form of space heating during the winter months to ensure worker comfort. Heat may be provided using a forced air central heating system that warms and circu lates the air throughout the maintenance facility or uti lizes an air-to-air heat exchanger. Localized space heating is another method for heating a maintenance facility. Localized space heating is typically accomplished using gas-fired infrared direct radiation or tube-type heaters, gas- or propane-fired devices equipped with fans, or elec tric infrared heating units.
Most of these types of heating apparatus are either mounted to the walls of the facility or suspended from the ceiling. Portable heaters used to provide supplemental heat in specific areas are typically placed on the floor. A facility that services both conventional and CNG vehicles needs ventilation systems to address conventional fuel vapors as well as natural gas releases. system that was designed to manage conventional fuel vapors or must provide liquid fuel code compliance in the design of the new ventilation system.
Rare exceptions may be granted by the AHJ to allow the existing ventila tion fans to be used as long as they are compliant with natural gas use and equipped with automatic dampers to close off the flow from floor level and open the pickup points at the ceiling level. Codes and regulations require that specific conditions be met for both heaters and heating systems. Classification of the facility as either a major repair or minor repair category is also an important factor. NFPA 30A: Heating equipment with open flames or exposed surfaces with a temperature above 750°F cannot be placed in areas that may experience a creditable release.
This includes all heating devices in a major repair garage. For major repair garages, NFPA 30A states that heating equipment with open flames or exposed surfaces that have a temperature in excess of 750°F shall not be permitted in areas that may experience a creditable release. For practi cal reasons, all heating devices in a major repair garage are subject to this limitation. Although not specifically stated, these same concerns and design approaches are also generally applied to minor repair garages. Most existing heating systems, except forced-air types, present specific challenges for CNG vehicle mainte nance facility compliance.
For flame-fired heaters, the flame itself is an ignition source. For gas-fired infrared direct radiation heaters, even for those where the flame is contained within the heating elements, the surface temperature of the radiant heating elements that exceed 750°F present a potential ignition source. Electric heaters that employ heating coils and a fan may or may not be compliant depending upon the operating temperatures reached by the heating coils. Figures 18 – 21 depict various types of space heating equipment commonly found in maintenance facilities that would need to be replaced, modified, or eliminated. Figure 17. Conventional fuel maintenance facility ventilation pickup points.
Photo courtesy of Gladstein, Neandross & Associates, NREL 44699 Regardless of the ventilation system selected, it must be designed by a registered/licensed engineer. Calculations showing the volume of air moved are required on the final design drawings. SEPTEMBER 2017 15