PreparingMaintenanceFacilities
For
AlternativeFueledVehicles
In the interest of reducing costs and meeting more stringent environmental regulations, fleet operators, both public and private, are moving towards changing their fleets from gasoline/diesel power to alternative fuels including natural gas, propane and hydrogen. With the introduction of these new fuels, the fueling stations and maintenance facilities normally need to be upgraded. At the maintenance facilities the potential concern lies with the alternative fuel containing vehicles themselves, but at the fueling stations the dangers could be the vehicles or the storage/fueling equipment. Maintenance facilities require gas and flame detectors in areas where the vehicle containing the alternative fuel could be located such as the work bays, paint shops, chassis wash, tire shop, fuel/dynamometer building or the CNG compressor area. Many Codes and Regulations including the International Fire Code and numerous NFPA codes are often applicable in these applications. In addition to the standard safety requirements established by the local fire department, most facilities require various agency approvals for the gas detection system placed in these areas. The gas sensors and control system normally need approval from FM, CSA, UL or other NRTL approved agencies. The monitoring philosophy is to react to the hazardous gas leak by providing dispersion and dilute with ventilation. They also require control and management of any ignition source near the location of the potential accidental discharge of gas. Finally, the owners/operators must determine the cost of ownership of a hazardous gas detection
system including, cost of installation, maintenance and operation.
What are Alternative Fuels?
There are three major types of Alternative Fuels: Natural Gas, Propane and Hydrogen. Natural Gas or Methane (CH4) is odorless and lighter than air with a specific gravity of about 60% of air which means the release of this gas in an enclosed space will migrate to the highest point. The explosive range of methane is 5% to 15% by volume, so it will take at least 5% methane in a room to be explosive. We call this point the 100% Lower Explosive Level. If there is too much methane in the room, for example if it is above 15% by volume, it is too rich and not explosive. Natural gas can be found in two forms for transportation. Compressed Natural Gas (CNG) is methane compressed to 3000 PSI to 4000 PSI at normal temperature. CNG’s storage vessels are specialized and require certification for use. Storage tanks on a vehicle maybe located on top, on the side, or behind the cab. Liquid Natural Gas (LNG) is at atmospheric pressure but refrigerated to -260° F which changes the gas to a liquid state. It requires smaller storage containers than CNG, but these storage vessels are also specialized to keep the fuel at a low temperature and therefor liquid. CNG is more commonly used for short-haul vehicles while LNG is more often used in long-haul vehicles. Hydrogen (H2) is odorless and also lighter than air with a specific gravity of 7% of air, and will also seek the highest point if released in an enclosed area, but it has a much larger explosive range from 4% by volume (100% LEL) to 75% by volume. It is a manufactured fuel and is stored at pressures of 8000 PSI to 10,000 PSI. As a manufactured fuel it is used in two applications: as the catalyst in a Fuel cell or as an ignition fuel. There are not many hydrogen vehicles in use today. Propane is also an odorless gas but has a specific gravity of 150% of air. It is a heavy gas and will seek low spaces for collection. All Propane has a chemical added to make it smell and has a small explosive range from 2% by volume (100% LEL) to around 10% by volume. As a transportation fuel it is very good and quite prevalent. It is also a manufacture fuel requiring specialize storage vessels and handling techniques. Codes and Regulations
Alternative fuel vehicle maintenance and refueling facilities are regulated by International, National and Local regulations. The primary standards that are important for the facility design are provided by the NFPA (National Fire Protection Association) and ICC (International Codes Council). The LAHJ (Local Authority having Jurisdiction) is the regulatory agent that may adopt or expand on these codes and determine which regulations are applicable to the facility. The key codes that affect an Alternative Fueled Vehicle Maintenance Facility are: 
International Fire Code IFC 2012 o 2311.7.1.1 Design. Ventilation shall be by a continuous mechanical ventilation system or
by a mechanical ventilation system activated by a continuously monitoring natural gas
detection system or, for hydrogen, a continuously monitoring flammable gas detection
system, each activating at a gas concentration of not more than 25 percent of the lower
flammable limit (LFL). In all cases, the system shall shut down the fueling system in the
event of failure of the ventilation system. o 2311.7.2 Gas detection system. Repair garages used for repair of vehicles fueled by nonodorized gases, such as hydrogen and non-odorized LNG, shall be provided with a
flammable gas detection system.
o 2311.7.2.1 System design.
The flammable gas detection system shall be listed or approved and shall be calibrated to
the types of fuels or gases used by vehicles to be repaired. The gas detection system shall
be designed to activate when the level of flammable gas exceeds 25 percent of the lower
flammable limit (LFL). Gas detection shall also be provided in lubrication or chassis
service pits of repair garages used for repairing non-odorized LNG-fueled vehicles.
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o 2311.7.2.2 Operation.
Activation of the gas detection system shall result in all the following:
 1. Initiation of distinct audible and visual alarm signals in the repair garage.
 2. Deactivation of all heating systems located in the repair garage.
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3. Activation of the mechanical ventilation system, when the system is interlocked
with gas detection.
NFPA 30A (2012) Motor Fuel Dispensing Facilities and Repair Garages NFPA 52 (2013) Vehicle Gaseous Fuel Systems Code NFPA 88A (2011) Standards for Parking Structures NFPA 70 2014 National Electric Code® NFPA 59A 2013 Standard for the Production, Storage and Handling of Liquefied Natural Gas (LNG) Note that the ICC and NFPA codes, if adopted, are adopted voluntarily by states and enforced by the local Authority Having Jurisdiction (AHJ).Additional codes may be referenced during the development of the LAHJ requirements. Design Considerations
When designing the facility it is important to take into considerations various design requirements based upon the codes and regulations. It is also necessary to determine the scope of work being conducted in the facility. Whether major or minor work is being performed is relevant regarding the codes, however, they are not particularly clear on the definition of major vs. minor work and it really is up to the AHJ to decide. One AHJ stated that if it takes a wrench, it is major! Also take into consideration the layout of the environment such as: 
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How open is the building? What natural ventilation exists? What other structures and buildings surround the building? What is the security of the building? What ignition sources exist in the building? And finally you need to consider the geographic and climate factors. Heavy duty ventilation of a building in the northern states would result in high energy costs during the winter. Gas Detection
The two primary choices for gas detection are portable detectors versus fixed detectors. Since the codes call for the gas detection system to 1) activate and alarm 2) deactivate heating system and 3) activate ventilation system, the only answer for a maintenance facility is a fixed gas detection system. A controller based gas detection system has the advantages of control and interface from a single point with minimal wiring costs, simpler calibration and the ability to have third party approval for the complete system. Controller based systems gives the operator greater control over the operation, being able to perform different control operations for different zones and having a central point to view detector functionality, usually via a user-friendly touch panel display. Due to the extensive codes and regulations involved in this situation, it is necessary that the sensors have third party approval, in particular Factory Mutual (FM) approval. In addition, many AHJ require not only third party approval for the pertaining to operation in hazardous locations but also performance approval showing that the sensors and control system operate according to code. Remember that NFPA 30A states that in an Alternative Fueled Vehicle Facility that the top 18 inches of ceiling area are considered to be Class 1, Division 2 hazardous areas so FM approval is mandatory for sensors located in this area. There are two types of sensors used to monitor for combustible gases. A Catalytic Bead sensor can monitor for both Natural Gas and Hydrogen. An infrared sensor can monitor for Natural Gas, but not Hydrogen. The calibration frequency for infrared sensors tends to be longer and as a result they require lower maintenance, but both sensors can have FM approval. When installing gas sensors, be sure to mount them in the proper locations as specified by your design engineer and AHJ. Remember that Natural Gas and Hydrogen are lighter than air so their sensors should be mounted close to the ceiling. Propane is heavier than air and thus the sensors must be mounted closer to the ground. Use common sense in determining mounting locations, like mount the sensor between the obvious source of the gas and the source of ignition, not directly in front of the ventilation fan. Alarm and Notification
Code requirements call for alarm when the hazardous gas reaches 25% LEL of the combustible level. The visual alarm must be visible from all points and the audible alarm heard to all people. It also must also be ADA compliant. Working with the AHJ will determine the proper evacuation and “safe to return” policies. Note that audible and visual alarms are not the same as a “Fire Alarm.” Auto dialers may also be installed where required. Mitigation
What is mitigation? It is the efforts taken to reduce loss of life and property by lessening the impact of the hazardous situation. The key mitigation for a release of combustible gas in a maintenance facility is to remove the gas! This is usually performed by proper and powerful ventilation. Under normal situations there should be a natural air flow occurring. The office areas will typically have a higher pressurization to prevent the entrance of hazardous and toxic fumes into a compact area. The designer of the ventilation system needs to make sure that make-up air is available either via the HVAC system or doors and vents. Most proper ventilation systems utilize a “push/pull” design with air handling units (AHU) pushing air into the building and exhaust fans pulling the air from the building and exhausting to the atmosphere. Normal day to day operation will have the fans on low speed to continuously refresh the air. During emergency situations when activated by the gas detection system the ventilation system increases the air flow to change the volume of air eight times each 60-minutes which is about 45% more than normal volume. Cost of Ownership
The proper design of any facility requires the designer to consider the cost of ownership for the total package. In terms of the ventilation the designer needs to take into consideration the cost of moving the air and the cost of heating the air moved. Equipment costs can range from $75K to $150K per bay and annual maintenance costs can be from $25 to $150 per sensor, depending upon the system design accessibility and other requirements. Summary
It is important that management realizes that the refueling and maintenance facility requirements will be different for alternative fueled vehicles. It is also vital that project planners take into consideration the type of fuel being used, use of the facility, local and national regulatory requirements, safety of the people and property, alarm and notification requirements, ventilation requirements and the total cost of ownership. Work with your design engineer and the local Authority Having Jurisdiction to determine what is necessary for your specific site. Author: Corey Miller, Alternative Fuel Market Specialist, Sierra Monitor Corporation Corey Miller is an Electrical Engineering Graduate from DeVry University. He has worked in the instrumentation field for the last 28 years and spent the last 15 years building Alternative Fuel Stations and modifying maintenance facilities to handle alternative fueled vehicles.