EMERGENCY PROCEDURES NATURAL GAS December 11, 2014 NATURAL GAS EMERGENCIES AND FIRES 1. INTRODUCTION

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1 December 11, 2014 EMERGENCIES AND FIRES 1. INTRODUCTION Gas emergencies can pose a great risk to FDNY members and the civilians we protect. This bulletin discusses the properties of natural gas, the distribution system found throughout the City, and how to mitigate the various types of gas emergencies the FDNY responds to on a daily basis. Natural gas can be found anywhere in the city. Typically, it is found in the following applications: Furnaces and Boilers Hot water heaters Stoves Ovens Dryers Barbecues Vehicles (Compressed Natural Gas) Fireplaces Outside Decorative Lighting Refrigeration Air Conditioners - large commercial units Window/Wall-Mounted Gas Heaters (see Photos 1 & 1a) Photo 1-Window-Mounted Gas Heater Photo 1a-Wall-Mounted Gas Heater Con Ed provides gas service to: Manhattan The Bronx The following sections of Queens: Astoria, Long Island City, College Point, Whitestone, Malba, Flushing, Fresh Meadows, Glen Oaks, Douglaston, parts of Sunnyside and Woodside, Little Neck, Bellerose, Floral Park, Roosevelt Island and Governors Island 1

2 National Grid provides gas service to: Brooklyn Staten Island Sections of Queens not covered by Con Ed Con Edison and National Grid also deliver above and below-ground electric. Con Edison also delivers steam. Although this bulletin deals exclusively with gas emergencies, all utilities, including water and sewer, are intertwined underground and a serious underground incident may involve multiple utilities. If called to a known release of gas, gas fire or explosion; have the appropriate gas utility respond. 2. PROPERTIES OF Natural gas is comprised mainly of methane but also contains ethane, propane and nitrogen. Colorless Odorless o Mercaptan is added to natural gas, giving it a distinctive rotten egg odor. o Mercaptan can be removed from natural gas as it passes through soil. It can also be masked by other odors, or stripped by other chemicals. This process is known as odor fade. o You can become desensitized to the odorant over time and may no longer smell it, even if natural gas is still present. o Always test for the presence of natural gas with a combustible gas detector. Lighter Than Air (rise in air) The Vapor Density (Relative Gas Density) is depending on the mixture and percentage of Methane and other ingredients. Explosive Range is 5% - 15% o If natural gas in the explosive range ignites in a confined location, it will explode with destructive force. o When unconfined (outdoors): natural gas will ignite, not explode. Ignition Temperature Degrees Fahrenheit Non-Toxic Asphyxiant - While non-toxic, natural gas in sufficient quantity can displace the oxygen in an enclosed space and cause asphyxiation. 2 Rev. 04/09/15

3 3. GAS DELIVERY SYSTEM 3.1 GAS PRESSURE Natural gas is delivered via pipeline to New York City at approximately 700 to 1400 psi. Pressure is regulated down to psi for transmission gas mains and then regulated to lower pressures for distribution mains. Distribution gas mains are run under the street and deliver either: o o o High pressure (60-90 psi) Medium pressure (3-15 psi) Low pressure (¼ psi) Gas service pipes branch off of the distribution mains to deliver gas to individual customers. o High and medium pressure gas is regulated down to ¼ psi before it passes through the customer s meter. o A minority of customers, particularly industrial and commercial facilities, may use full line pressure. 3.2 GAS PIPE COMPOSITION Transmission Mains: Steel High Pressure Distribution Mains: Steel, Plastic Medium Pressure Distribution Mains: Steel, Plastic or Cast Iron Low Pressure Distribution Mains: Steel, Plastic or Cast Iron Gas Service Piping: Steel, Plastic or Copper o o Plastic and copper gas pipes are not allowed inside structures Plastic and copper may have been inserted in former steel services 3.3 GAS METERS Gas meters can supply individual occupancies or entire buildings. Gas meters supply gas to most customers at ¼ psi. o A few commercial customers receive gas at 1 to 3 psi. o There are a small number of large facilities that utilize full line pressure, especially for generation. 3

4 Regulators are usually located before the gas meter on high and medium pressure systems to reduce incoming gas pressure to ¼ psi, or higher as in the exception above. (Photo 2) Photo 2 High Pressure Gas Regulator Peck Vent - found on high pressure services. If the regulator fails, this safety valve vents excess gas to the exterior of the building. (Photo 3) Photo 3-Peck Vent 4

5 Single Master Meter - Some multi-occupancy buildings have only a single meter supplying gas to all occupancies. Shutting it down will shut the gas to the entire building. (Photo 4) Photo 4 Low Pressure Residential Master Meter Note the interior riser valves on the gas piping above the meter Some older apartment buildings may have individual gas meters located in each apartment served, and in some buildings the meters may be found in the public hallway. The presence of gas piping or meters in a public hallway requires a high priority referral (see BISP Manual Chapter 5, Reference 2.1) 3.4 SHUT OFF VALVES Most gas shutoffs are of the ¼ turn variety and can easily be shut off using the fork end of a Halligan tool (Figure 1), vice grips, or pliers to turn the wing cock valve ¼ turn counter-clockwise. When the key operating nut is parallel to the piping, it is in the open position (Figure 2). When it is perpendicular to the piping, it is in the closed position (Figure 3). 5

6 Figure 1 Halligan tool, vice grips, or pliers can be used to shut the ¼ turn gas valve counter-clockwise Figure 2 Figure 3 Gas Valve Open Gas Valve Closed Do not force a gas valve; it could break causing a new gas leak at the valve location. When it is necessary to shut a gas valve, shut the valve closest to the leak, when possible. In older installations where large amounts of gas are used and the piping into the consumer s building is 3 or larger, a simple wheel-handled gate valve may be found as the main shutoff valve. (Photo 5) This valve will be located just inside the building wall where the service enters the building and can vary in size from approximately 3 in diameter to approximately 10 in diameter. These older, multiple-turn, wheel-handle valves, resemble water valves or outside stem and yoke (OS&Y) valves in the closed position. Care should be exercised that one is not mistaken for the other. 6

7 Photo 5 Wheel-Handle Main Gas Shutoff Valve 3.5 THE PRIORITY ORDER OF VALVE SHUTDOWN: 1) Appliance Valve - Shut this valve first, when possible. It is usually located behind or alongside the gas appliance and connected by hard piping or flexible metal tubing. The appliance may have to be moved to access it. When the valve is damaged, missing, stuck, or inaccessible, shut the meter valve. 2) Meter - A building can have multiple meters or a single master meter. A. Meter Valve - There will be a ¼ turn meter valve located just before each meter. When the valve is not accessible or is stuck, proceed as outlined below. B. Interior Gas Riser Valve - Often there are interior gas riser valves coming off the master meter, typically found in the ceiling of the basement, which can be used to isolate a section of the building instead of shutting service to the entire building. A large building may have a meter for each occupancy or a single master meter for the entire building (Photo 4). Shutting down the ¼ turn valve at the master meter will shut the gas to the entire building. Note: When possible, avoid shutting the master meter. To restore service to a large building or complex once the gas is shut off, the utility company must access each affected apartment, shut the gas appliances, pressure test the piping, and then relight the pilot lights. (If the building is large, it may take several weeks to restore service to the building. This process is not only time consuming and a great inconvenience to occupants, but it is also very expensive.) 7

8 C. Master Meter Valve When possible, notify the utility company of your intention prior to shutting a master meter and inquire as to possible alternatives. A single master meter may have a second master meter next to it. This second meter is used in the event there is a malfunction in the meter in use. The utility company can switch service over to the second meter without disrupting service to the building. Consult with the gas utility to ensure the correct meter is being shut down. When the meter is inaccessible or damaged as a result of a fire, the gas supply to the building may have to be shut at the head of service valve. 3) Head of Service Valve (a.k.a. Building Service Valve) (Photo 6) This valve is found just inside the building where the gas service enters. Most of these are ¼ turn valves. When the meter or meters are located outside, the valve will be before the meter(s). Photo 6 Figure 4 Head of Service (Building Service) Valve Old High Pressure Shutoff Note: On some older, high pressure gas services (Con Ed System), the main shut-off valve will require approximately 4½ to 5 clockwise turns of the operating nut to shut off the gas flow. (Figure 4) 8

9 4) Exterior Gas Riser Valve - Gas riser valves are ¼ turn valves located on the gas riser outside of the building before any exterior meters. All external meter installations will have a riser valve installed prior to the meter. When a curb valve is found, look for the exterior riser valve. This valve may be present outside, even when meters are installed inside the building. (Photo 7) Exterior Gas Riser Valve Photo 7 The exterior gas riser valve is located on the riser before the bank of outside meters. Each meter also has its own shut-off valve. 5) Curb Valve - (Photo 8) The curb valve is usually found on the sidewalk side of the curb and shuts the gas supply to the entire building. It is usually recessed in from the curb and is covered with a 4 X 4 square or round brittle concrete or steel cover which may be sitting on top of a plastic or wooden plate. It is shut using the gas key found on Department apparatus. To shut the valve, remove or break the cover and plate, attach the proper end of the gas key onto the valve, and, in most cases, turn the key ¼ turn clockwise. Before shutting the valve, look into the valve box. When the valve operating nut is white, close it gently. A white valve is plastic and easily broken by excess force. Note: Before turning the key, place chalk or some other mark near the valve to indicate your start point. This will assist in noting when a ¼ turn is completed. National Grid supplies a white plastic insert for shutting down plastic valves. Con Ed uses the gas key as is to shut plastic valves. Long Service - On the National Grid system, the curb valve is sometimes located across the street from the building it supplies, and may be found in the street. These curb valves can be identified by an arrow cast into the cover pointing to the building it supplies. These also require a ¼ turn clockwise to close. (Photo 9) 9

10 Photo 8 Photo 9 Curb Valve National Grid Long Service Curb Valve The curb valve may have been covered with concrete or grass and not visible. Some older curb valves are gated and will require multiple turns to close. When a ¼ turn does not shut the gas off, continue to turn the valve until resistance is met. This may occur between 7½ to 15 full turns. Do not turn the valve more than 15 times. Note: Before turning the key, place chalk or some other mark near the valve to indicate your start point. This will enable you to note how many turns have been made as well as where a ¼ turn would be if the stop point is broken and 15 turns have been made. Gas Shut-off Key - The gas shut-off key consists of a long shaft with a uniquely shaped wrench socket on either end (Photos 10, 11, 12) that is placed onto the curb valve s operating nut. Before using the key, determine which end is suitable for the valve that is being shut down. Photo 10 Photo 11 10

11 Photo 12 Firefighters close a curb valve using a gas shutoff key and a Halligan tool for leverage 6) Street Valve (a.k.a. Line, Main, or Isolation Valve) - These valves are located on the street side of the curb. They can look like curb valves but control main gas lines running under the street. These valves are used to isolate large sections of the gas main. Members shall not operate street valves. On the National Grid system, these valve covers are identified by an ID number stamped on the North side of the cover, however, these numbers may be obscured. The cover may be round or square and come in a variety of sizes (typically 9 or larger). Shutting a single street valve may not stop the flow of gas as distribution piping can be fed from more than one direction. The utility company must refer to maps to determine which valves to shut. It may be necessary to shut several street valves, some possibly remote from the building or area with the gas emergency, in order to isolate a section of piping. o Shutting a street valve may disrupt gas service to a large area and/or critical locations. Gas service may not be restored to the area for several weeks. These valves are usually not present on low pressure gas systems. Stopping the flow of gas in a low pressure main will require the street mains to be excavated and stoppers installed, which may take several hours. Note: Members shall not operate street valves. Have the utility company shut all valves beyond the curb valve. 11

12 4. OPERATIONS 4.1 GENERAL Wear full PPE when operating at gas emergencies and wear the SCBA facepiece when operating in a gas atmosphere Do not position apparatus in what is or might become a hazardous area. Stage apparatus upwind, out of the path of the leaking gas, and at a safe distance. All units should stay out of the potential collapse or ignition zone. Do not park over manholes or sewer gratings as gas may be venting from these locations. Notify incoming units of the need to approach from upwind and designate a safe staging area. Ladder companies should take a preliminary safe position that will allow them access to the building. Engine companies should take hydrants in safe locations and prepare to stretch lines as necessary The apparatus is a source of ignition. When approaching an alarm location, if a strong gas odor is detected, stop the apparatus and take readings with a digital combustible gas meter Exclude vehicles and pedestrians from the potential danger area Take gas readings with all available gas detectors/meters (TIF 8800X, Altair, and Digital). When necessary, special call a unit with a digital gas meter if one is not already on scene, or request additional Haz-Mat resources Approach the building from the corner as an explosion will tend to blow walls directly outward Stand to the side of doors and windows when approaching or knocking Ignition sources: Doorbell - Knock on the door, do not ring the bell. Static electricity. o Walking on a carpeted floor can generate a static charge and result in a spark when a metal object is touched. o Gas flowing out of a broken plastic pipe generates static electricity which builds up on the inside and outside surface of the pipe. Coming near to or touching a leaking plastic gas pipe could result in a spark that ignites the escaping gas. (Photo 13) The gas utility has equipment to dissipate static electricity buildups. 12

13 Photo 13 Caution: Although easily folded, firefighters should not approach or attempt to fold a leaking plastic gas pipe Building light switches/electrical devices - Do NOT turn lights on/off or operate electrical devices until the area is properly vented, tested, and found safe. Telephones - desktop and cellular phones can generate a static spark. Heating/AC units - A furnace or boiler can provide an ignition source. Overhead and underground trains and other vehicles are potential sources of ignition. Traffic control boxes on light poles are a source of ignition. Fire Department issued flashlights are intrinsically safe. Non-FDNY issued flashlights, FDNY thermal imaging cameras, and Department fans are not. As a precaution, turn flashlights on before entering a building or an explosive atmosphere, and do not shut them off until back in a safe atmosphere Pulling an electric meter or opening a breaker can generate a spark. Have the power to a gas filled building removed at the pole or manhole by the utility company. Before removing power, determine if there is emergency power or a generator, which, when power is cut, will activate and provide an ignition source. When it can be done safely, have emergency power disabled before cutting power to the building Gas can migrate underground through the soil, electric conduit, and sewer pipes. If you cannot find the source of an indoor leak, take readings at sewers and manholes. Check sewers and manholes at outdoor leaks to determine where and how the gas is migrating, and the danger area. When the gas is migrating through the soil, be alert to the potential for it to accumulate in underground void spaces, including any space under a concrete slab floor, around utility pipe runs, etc. The utility company can track gas movement through the ground by inserting probes through the concrete and pavement If gas readings are obtained in ELECTRIC, SEWER, or any other utility MANHOLE(S), the surrounding structures must be checked. 13

14 When operating at the scene of a serious gas incident and gas readings are found in an ELECTRIC MANHOLE: Identity the buildings(s) being supplied electricity by the involved manhole(s), through the utility company representatives, or, if not on scene, from the utility company through the FDNY dispatcher. Utilize this information to prioritize the checking of buildings for the presence of gas When operating at the scene of a serious gas incident and gas readings are found inside buildings where the electricity enters the building (Electric Point of Entry or POE): Identify the location of the manhole that supplies electricity to the building and any other building(s) it supplies. This information can be obtained through the utility company representatives, or, if not on scene, from the utility company through the FDNY dispatcher. Utilize this information to prioritize the checking of buildings for the presence of gas Removal of MANHOLE COVERS by FDNY personnel may reduce the infiltration of gas into surrounding properties and shall be done only in compliance with the following guidelines: SEWER MANHOLE COVERS Removal of SEWER MANHOLE covers can be performed by FDNY personnel with the approval of an on-scene Chief Officer. ELECTRIC MANHOLE COVERS Removal of ELECTRIC MANHOLE covers by FDNY personnel may be performed only when requested by a utility company gas representative on the scene and approved by an on-scene Chief Officer. Prior to requesting FDNY personnel to remove a manhole cover, the utility company gas representative must test the cover for stray voltage. If the cover is found to be free of stray voltage, FDNY personnel may remove the cover upon the orders of an on-scene Chief Officer in conjunction with the utility company gas representative. Round Manhole covers should be removed by two firefighters utilizing manhole hooks. Battalion vehicles carry two manhole hooks for use in removing electric manhole covers. DO NOT pull rectangular or square electric manhole covers. DO NOT pull any electric manhole covers if there is a manhole fire in the area or if smoking or arcing is observed in an electric manhole or transformer vault. If in doubt as to which type of manhole is affected, or if there is obvious smoke under pressure or electric arcing, DO NOT remove the manhole cover. 14

15 Any time the decision is made to remove a manhole cover(s) the Chief Officer ordering such removal shall ensure the area around the manhole(s) is properly cordoned off to identify the hazard. Note: This policy relates to operations with both Con Edison and National Grid Gas Personnel When investigating any odor of gas (indoor or outdoor), be alert to the presence of utility trucks/workers, construction sites, or recently patched sections of pavement in the area, indicating recent or ongoing work and the potential source of the leak Once you turn a gas valve off, never turn it back on. Turning a gas valve back on will result in gas leaks at the stove, boiler, and other pilot lights in the building as well as at the location of any damaged piping The Incident Commander (IC) shall notify the responsible utility company via the borough dispatcher any time a natural gas valve has been shut down or operated by the FDNY. The type and location of the valve shall be included in this notification. Units are not required to remain on the scene awaiting the utility s arrival unless conditions indicate and/or the IC requests an immediate response. The Fire Department has been requested by the New York State Department of Public Service to notify the appropriate utility company in certain instances where the Fire Department responded to a natural gas related incident. The Public Service Commission requires utility companies to conduct an investigation when the following occurs: o Injuries or fatalities are sustained from carbon monoxide poisoning during an emergency in a building where natural gas may have been a contributing factor. o Any fire or emergency where natural gas may have been a contributing factor. 4.2 ADDITIONAL CONSIDERATIONS A burst water main can undermine and cause a break in underground gas piping. Notify the gas utility of water main breaks A burning or arcing electrical manhole can burn through a nearby metal or plastic gas line, causing and igniting a gas leak. If you smell gas or suspect its involvement in a manhole fire, request the response of the gas utility in addition to the electric utility The arc from fallen high voltage electric wires can burn through asphalt or concrete down to buried gas lines. The damage this causes to the metal or plastic gas lines can result in a leak which can be ignited by the arcing wire. If you smell gas or suspect its involvement, request the response of the gas utility in addition to the electric utility Always consider the possibility that an outdoor gas leak is migrating into buildings and other structures. 15

16 4.3 MINOR INDOOR GAS LEAK: Indications Slight or no odor of gas. Low readings on digital gas meters. Tactics Observe all general procedures listed in Section 4.1. Locate the source of the gas leak. If gas is leaking indoors and not burning, shut the gas supply as close to the source as possible and ventilate the area. o Ventilate buildings from the top down. o Department fans are not intrinsically safe and should not be used to vent gas. o A fog nozzle may be used for venting, if necessary. If the leaking gas is burning, allow it to burn until the gas supply is shut off. When the burning gas is extinguished before the supply is shut off, it will continue to discharge, and may explode or suddenly re-ignite if it comes in contact with a source of ignition. Combustible material near the burning gas should be wet down while waiting for the gas supply to be shut off. A leak or break in low pressure gas piping may be stopped or greatly diminished by taping, or stuffing rags, paper, etc., into the break. This tactic will not work on high pressure piping, and leaking plastic pipe should not be touched or approached. Operate with a minimum of personnel in the gas atmosphere. Notify the utility company of all gas valves that have been shut. 16

17 Other Considerations Old gas lines were used for illumination. These lines were sealed with wax and over time this wax deteriorates resulting in a gas leak. These types of leaks can be difficult to locate. (Photo 14) Photo 14 Old gas lighting pipes are visible on this ceiling. Direct vent boilers and hot water heaters have become prevalent throughout the city. They may be located anywhere within a structure and are vented by a short length of pipe through an exterior wall. At fires, the presence of window or wall-mounted gas heating units must be communicated to the Incident Commander and their gas supply shut down. (Photos 1, 1a) 4.4 MAJOR INDOOR GAS LEAK: Indicators Heavy odor of gas, unless the mercaptan has been scrubbed out. High readings on digital combustible gas meters. Tactics Observe all general procedures listed in Section 4.1. Transmit the appropriate signals. Notify the gas utility to respond and request an ETA. Evacuate the building when necessary. Locate the source of the gas leak when it is safe to do so. 17

18 Shut the gas valve as close to the source as possible, and ventilate when it is safe to do so. o o o Start venting at the upper levels of the building when possible, and then work down to the first floor and out of the building. Note: When gas levels are above the flammable limits, they will drop into the flammable range as you ventilate. Department fans are not intrinsically safe and should not be used to vent gas. A fog nozzle may be used for venting, if necessary. Check at least three exposures on each side of the affected occupancies for the presence of a gas odor or leak. Check above and below the suspected leak. Evacuate and ventilate as necessary. Consider closing windows and shutting ventilation systems in nearby buildings. 4.5 OUTDOOR GAS LEAK: Indicators A heavy gas odor in the area. It may be intermittent, especially on a windy day. There may be an opaque cloud rising from the ground at the site of the leak. Dirt and debris may be seen blowing into the air from an excavation. This would indicate a high pressure leak. A loud roaring sound indicates a high pressure leak. Tactics Observe all general procedures listed in Section 4.1. Transmit the appropriate signals. Notify the gas utility to respond and request an ETA. Engine companies should position at a safe hydrant and stretch precautionary lines to a safe location out of the gas cloud to protect exposures, provide ventilation, and dissipate the gas cloud. Search the area for victims and locate the leak. Assist any injured civilians and evacuate anyone in the danger area. Search and evacuate surrounding structures as needed. Notify the dispatcher of the location and extent of the leak and, when available, whether it is low pressure or high pressure. When gas is burning, do not attempt to extinguish it. Protect exposures with fog streams and wait for the utility company to stop the gas flow. When the escaping gas is not burning, fog streams can be used to dissipate the escaping gas or to direct it away from threatened exposures. 18

19 When the leaking pipe is in an excavation, avoid filling the excavation with water. Doing so will only hamper the repair process. In addition, this will flood the gas mains and services which could knock out pilot lights and lead to a serious gas accumulation problem downstream. Remove all sources of ignition when safety permits. Look for sources of ignition such as decorative gas street lamps, barbecues, overhead trains, sparks from fireplaces, and construction equipment. Remove these sources of ignition when it is safe to do so remembering that shutting down construction equipment and other vehicles can cause a spark. Continuously monitor surrounding structures, sewers, and manholes for gas infiltration. Other Considerations Gas from a leaking pipe may travel some distance before finding a place to surface as pavement, snow, or frozen ground can trap it underground. Exterior gas leaks can occur at construction sites, during electrical emergencies, at steam leaks, and as the result of a flood or water main break. Gas piping is placed alongside water, steam, and electrical lines. When operating at any of these types of emergencies, be aware that they may affect each other. Damage to a gas pipe at a construction site may result in additional damage to the gas pipe at other locations. For example, when a backhoe pulls and/or breaks a gas service line, it may also have dislodged the service line from the building, separated a coupling, and/or pulled the pipe from the gas main in the street. The result would be a gas leak where the backhoe was operating, another leak at the building line or in the building, and still another one at a coupling or where the service line connects to the street main. 4.6 UNDERGROUND GAS LEAK Indicators Inability to locate source of gas odor in building. Inability to locate source of outdoor gas odor. Gas odor coming from sewers or manholes. Tactics Observe all general procedures listed in Section 4.1. Transmit the appropriate signals. Have the gas utility respond and request an ETA. Take gas readings in buildings, sewers and manholes. Implement procedures listed in Sections as necessary based on the conditions encountered. 19

20 5. METERS 5.1 TIF 8800X Combustible Gas Detector See Addendum 3. Carried by all Battalions and Ladder Companies. Should be used in conjunction with the Altair Digital Gas Meter. Can be used to pinpoint small leaks but does not indicate how hazardous the atmosphere is. 5.2 MSA Altair Digital Gas Meter See Addendum 2. Carried by all Ladder Companies. Should be used in conjunction with the TIF 8800X Detector. Will give a digital readout of the Lower Explosive Limit (LEL) for combustible gas. 5.3 Digital Combustible Gas Indicator (DCGI) Carried by all SOC Companies, SOC Support Ladder Companies, and Haz-Mat Technician Units. Calibrated to display the percentage of the lower explosive limit (LEL) of any flammable gas present. The DCGIs and Altair currently in use by the Department sound an alarm at 10% LEL, the indoor action level, and a different alarm at 20% LEL, the outdoor action level. The FDNY, in compliance with OSHA standards, will begin evacuation at the 10% LEL level if we are unable to reduce the LEL level immediately (ventilation, shutting of valves, etc.). It is important to keep in mind that the reading on the meter represents the level of flammable vapors at the specific location of the meter only. The environment closer to the source of the leak (or in other areas where the gas may have accumulated) could contain a higher level of flammable vapors, possibly in excess of 100% of the LEL. Note: The utility company s meters are not calibrated the same as FDNY meters. The utility company s meters display the percent of gas in the air. When given a reading from any meter, be sure you know if it is given in % of LEL or % of gas in the air. (Table 1) 20 Rev. 02/26/15

21 Table 1 is used to convert the DCGI readout from % of LEL to % of gas in the air for natural gas. TABLE 1 Utility Meter %GAS in air %LEL Fire Department Meter Indoor Action Level Lower Explosive Limit Figure 5 is a graphical comparison of LEL to % of gas in the air. Percentage of Natural Gas in Air Measured by Utility Company 0% 5% 10% 15% 0.50% 2.5% Explosive range 10% 50% 0% 100 % 100% LEL equals 5% gas in air. Percentage of Lower Explosive Limit Measured by Five Star Meter Note: 10% LEL Is FDNY Action Level Diagram 2 Figure 5 6. PECK/RELIEF VENT The location of the curb valve for high pressure systems may be indicated on the peck/relief vents which are located on the exterior of the building. The vent is a device that will allow excess gas to be vented to the outside air if there is a malfunction of the pressure regulator valve in the high pressure system. There should normally be no odor of gas at a peck vent. If an odor is detected, you must investigate to determine the source. (Photo 15) 21

22 The following diagrams and methods outline how to utilize the code letters and numerals found on the gas vents to find the approximate location of the curb valves on the most common types of installations. Factors such as unusual construction, odd layout or location of the building, technical problems encountered by the utility company when installing the service piping, etc., may cause variations from the basic methods described herein. 6.1 CON EDISON CODING Photo 15-Peck Vent Showing Con Ed coding and measuring directions If the code reads 5-R-25, the following procedure should take place to locate the curb valve; starting at the left hand front corner of the house, as it is faced from the street, 5 feet would be measured off to the right. At that point 25 feet would be measured off at right angles toward the sidewalk. The curb valve should be located at this point. (Figure 6) Figure 6 Figure 6 Con Edison Peck Vent Location System 22

23 6.2 NATIONAL GRID CODING The National Grid Peck Vent coding system differs from Con Edison s system. National Grid uses two different systems. One method is used in the Rockaways and another in the rest of Queens, Brooklyn, and Staten Island. In the Rockaways, you will find the numerals and letters on the peck vent, or on a tag (Photo 16) hanging on the piping in the immediate area of the gas meter. If it reads L-30, R-25, M-10, then, starting at the left corner of house (facing it from street) an arc is inscribed with a radius of 30'. The same would be done from the right corner with a radius of 25'. Where these two arcs intersect, would be the location of the curb valve. Then, 10 feet at right angles from this curb valve, in the direction of the street, would be the location of the gas main pipe running in the street parallel to the curb. (Figure 7) Photo 16 National Grid peck vent coding on Metal Tag If the letters EFV are inscribed on the tag then there is no curb valve and where the lines meet denotes the location of an Excess Flow Valve which will automatically shut down the flow of gas when it senses an excess flow of gas. The Letters NC on the tag also indicate that there is no curb valve present. Figure 7 National Grid curb valve location system for the Rockaways 23

24 In the rest of the areas served by National Grid, excluding the Rockaways, there is a different coding system. It will read as follows: 15RLBW and 10FFW. o 15 RLBW indicates 15 feet right of the left building wall. o 10FFW indicates 10 feet from the buildings front wall. (Figure 8) Start at the left building wall and measure off 15 feet to the right. From this point, measure 10 feet at right angles toward the street. This is the approximate location of the curb valve. National Grid Figure 8 National Grid curb valve location system excluding the Rockaways 24