Are you interested in the considerations for garage and maintenance shops when using CNG & LPG? Learn about the considerations of using a garage to maintenance CNG & LPG and the guidelines that need to be followed.

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Understanding Applicable Codes and Requirements!
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There are a number of codes applicable to any vehicle repair or maintenance facility,
regardless of Fuel Type!
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International Code Council’s International Fire Code (IFC 2012)!
International Mechanical Code (IMC 2012)!
International Building Code (IBC 2012)!
National Fire Protection Association’s NFPA 30A (2012) Code for Motor Fuel!
Dispensing Facilities and Repair Garages!
NFPA 30 A 2012 Code for Motor Fuel Dispensing Facilities and Repair Garages!
NFPA 52 (2010) Vehicular Gaseous Fuel Systems Code!
NFPA 88A (2007) Standards for Parking Structures.!
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Ventilation Requirements!
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IMC (2012) Table 403.3!
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The International Mechanical Code (IMC 2012) Table 403.3 requires all vehicle repair
garages, regardless of fuel type or maintenance performed, to have a ventilation rate of
0.75 cfm/sqft of floor area.!
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NFPA 88A (2007) 5.3.2!
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NFPA 88A requires a ventilation rate of 1 cfm/sqft of floor area for enclosed parking
garages housing liquid and gaseous-fueled vehicle.!
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International Fire Code 2012 (IFC 2012) - Adopted for CNG Vehicles!
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Section 2311.7 of the International Fire Code covering Repair garages for vehicles
fueled by lighter-than-air fuels states very clearly that Repair garages for the conversion
and repair of vehicles which use CNG, liquefied natural gas (LNG), hydrogen or other
lighter-than-air motor fuels shall be in accordance with Sections 2311.7 through
2311.7.2.3 in addition to the other requirements of Section 2311.
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IFC 2012 (2311.7.1 Ventilation)
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Repair garages used for the repair of natural gas- or hydrogen-fueled vehicles shall be
provided with an approved mechanical ventilation system. The mechanical ventilation
system shall be in accordance with the International Mechanical Code and Sections
2311.7.1.1 and 2311.7.1.2.
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International Fire Code 2012 (IFC 2012) - Adopted for CNG Vehicles (continued)!
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IFC 2012 (2311.7.1.1 Design)
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Indoor locations shall be ventilated utilizing air supply inlets and exhaust outlets
arranged to provide uniform air movement to the extent practical. Inlets shall be
uniformly arranged on exterior walls near floor level. Outlets shall be located at the high
point of the room in exterior walls or the roof.
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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.
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The ventilation rate shall be at least 1 cubic foot per minute per 12 cubic feet [0.00139
m3 × (s • m3)] of room volume.
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Ventilation Requirements for Vehicle Repair Facilities
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International Fire Code IFC 2012 2311.7.1.2 Operation states that the existing
mechanical ventilation system shall operate continuously. This assumes that the
mechanical ventilation system in place is already compliant with the various mechanical
and fire code requirements as specified in section (A) of this report.
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There are two exceptions to this requirement.
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1. Interlock mechanical ventilation system with a gas detection system.
2. Interlock the mechanical ventilation system with the lighting circuit.
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Note: These exceptions are only applicable to odorized gases and shops classified as
major repair facilities (see chart)

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Gas Detection Systems
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International Fire Code 2311.7.2.1 System design.
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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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2311.7.2.1.1 Gas detection system components.
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Gas detection system control units shall be listed and labeled in accordance with UL
864 or UL 2017. Gas detectors shall be listed and labeled in accordance with UL 2075
for use with the gases and vapors being detected.
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2311.7.2.2 Operation.
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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.
3. Activation of the mechanical ventilation system, when the system is interlocked with
gas detection.
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2311.7.2.3 Failure of the gas detection system.
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Failure of the gas detection system shall result in the deactivation of the heating system,
activation of the mechanical ventilation system and where the system is interlocked with
gas detection and causes a trouble signal to sound in an approved location.
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Electrical Classifications NFPA 30A
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8.2.1* In major repair garages where CNG vehicles are re- paired or stored, the area within 455
mm (18 in.) of the ceiling shall be designated a Class I, Division 2 hazardous (classified)
location.
8.2.1 allows for one exception
Exception: In major repair garages, where ventilation equal to not less than four air changes per
hour is provided, this requirement shall not apply.
Explanation
The area 18” of below from the ceiling will remain an UN-CLASSIFIED area with no
modifications required as long as the area 18” or below from the is properly ventilated.
Specifically, the intake for the exhaust must be within 18 inches from the highest point of the
ceiling. The ventilation rate for this area should be 4-5 air exchanges per hour.
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Sources of Ignition
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NFPA 30 A 7.6.6 states where major repairs are conducted on CNG-fueled vehicles or
LNG-fueled vehicles, open flame heaters or heating equipment with exposed surfaces
having a temperature in excess of 399°C (750°F) shall not be permitted in areas subject
to ignitible concentrations of gas.
IFC – No specific requirements
Note 1: Minor repair garages are facilities where work is not performed on the fuel
system and work is limited to exchange of parts and maintenance requiring no open
flame or welding. All other garages are defined as major repair garages.
Note 2: Determining ‘areas subject to ignitable concentrations of gas’ requires
understanding what a creditable release of CNG (the hazard) in the facility and then
determining the probability of where an ignitable may be present.
Both the IFC and NFPA 30A have a number of requirements addressing sources of
ignition for liquid fuel garages. Only NFPA 30A has additional requirements for CNG
vehicle major repair garages.
The requirement is directed at restricting open flame heaters and any heating
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equipment with exposed surfaces with temperatures above 750 F from any area
subject to ignitable concentrations of natural gas.
The conservative approach would be to eliminate heating equipment of these types
from the major repair garage. It would take an analysis of the potential credible natural
gas releases and modeling of the possible concentrations of ignitable gas within the
facility in order to safely place these types of heaters in safe areas. This analysis is
typically beyond normal heating design work and would be subject to approval by the
AHJ on a case-by-case basis.
The common sense approach would to remove any source of ignition from the classified
area (18” or below from the ceiling) and to tie the ignition source (all heaters) directly to
a methane monitoring system that would shut down all heaters in the event of an alarm
condition as specified in section E.
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Preparation of Vehicle for Repair - Code Requirements
IFC 2211.5 is the only code requirement that addresses mitigation of the assumed
hazards from releases of natural gas byIsolating the CNG cylinders from the balance of
the fuel system by valve closures prior to maintenance.
Operating the NGV until it stalls due to low fuel pressure in the system can further
reduce the possible release volume with the cylinder valves closed.
IFC 2211.5 also requires that the fuel system on the NGV be tested for leakage by
appropriate methods if there is a concern that the fuel system has experienced any
damage. If damage is suspected the vehicle may need to be de-fueled prior to any
maintenance.
Best Practices and Procedural Recommendations
1. Vehicles parked after being brought into the maintenance area shall have the 1/4
turn valve turned to the off position. This will cut off the supply of fuel to the engine.
2. Vehicles parked in the parking garage or maintenance area unattended or overnight
should have the CNG storage cylinders turned to the off position and the 1/4 turn
valve closed. This will cut off the supply of fuel to the fuel module from the cylinders
and to the engine and greatly minimize unintentional release of fuel to the Pressure
Relief Valve only (located on each cylinder).
3. When welding or torching on or near a CNG vehicle both the main supply valves on
each cylinder and the 1/4 turn valve should be closed and the engine should be run
to starvation (before closing the 1/4 turn valve) thus greatly reducing the risk of
ignition.
4. When maintaining any portion of the fuel system, including filter maintenance or fuel
system repair both the main supply valves and 1/4 turn valves should be closed and
the engine should be run to starvation (before closing the 1/4 turn valve).
5. Under no circumstances shall fuel system leaks be diagnosed inside the repair
facility. If a leak is suspected the location of the leak should be identified in a well
ventilated area and isolated prior to bringing the vehicle into the repair facility.
6. Under no circumstances shall a repair be attempted on a leak under pressure. Once
a leak is identified the fuel system should be completely isolated by closing the main
supply valves and running the engine to starvation prior to attempting any repair.