TAC #21: HANDLING GAS EMERGENCIES (NATURAL AND PROPANE)

SOP #21: Handling Gas Emergencies (Natural and Propane) Objectives

• Primary Objective: To provide a standardized procedure for safely handling gas leaks, both inside and outside of structures, for the Baltimore County Fire Department.

• Scope: This Standard Operational Procedure (SOP) covers both natural gas and propane gas emergencies.

• Decision-Making Simplified: The use of atmospheric monitoring equipment (meters) simplifies the “go/no go” decision-making process.

• Rescue Threshold: If a meter alarms, personnel should only “go” or enter the hazard zone if there is a rescue to be made of a live, viable victim.

Properties and Hazards of Natural Gas and Propane

• Shared Physical Characteristics: Both natural gas and propane are colorless, odorless, and highly flammable gases.

• Odorant Addition: To aid in detection, the gas company adds an odorant known as ethyl mercaptan.

  • Attenuation Risk: When gas travels through dirt or over long distances, it can lose the added odorant.

  • Olfactory Fatigue: The human nose can become sensitized (lose the ability to smell) to the odorant after prolonged exposure.

• Ignition Hazard: The ignition of either gas will result in a violent explosion.

• Flammability Ranges:

  • Natural Gas: Between $4-15\%$

  • Propane: Between $2.1-9.5\%$

• Vapor Density and Ventilation Requirements:

  • Natural Gas: Lighter than air; it will rise. Consequently, structures should be vented high.

  • Propane: Heavier than air; it will sink. Consequently, structures should be vented low.

• Liquefied Petroleum Gas (LPG) Composition: LPG is composed of a mixture of propane, propylene, butane, and butylenes.

• Migration Potential: Underground leaks permit gas to travel considerable distances. It may enter structures through foundations, around piping, or through various void spaces. Never underestimate the potential of a gas leak.

• Internal Ignition Sources: Common items inside a structure can trigger an explosion, including:

  • Turning on a light switch.

  • A telephone ringing.

  • A doorbell ringing.

  • The presence of a pilot light.

  • Static electricity generated by walking over carpeting.

Natural Gas Leak Inside a Structure: Response and Tactics

• Apparatus Positioning: The first arriving engine must position the apparatus at a minimum of $300\,\text{feet}$ from the structure. All other equipment should stage one block away.

• Operator in Charge (OIC) Responsibilities: Establish scene control, isolate the area, deny entry, and evacuate the structure.

• Collapse Zone Awareness: Anticipate a collapse zone. Any ignition will cause a violent explosion accompanied by collapse and debris.

• Rescue Operations: The second arriving engine assumes a position to allow for a water supply and prepares for rescue operations in the event of a catastrophic occurrence.

• Entry Crew Protocols:

  • Personnel must wear full turnout gear and Self-Contained Breathing Apparatus (SCBA).

  • Metering must begin in the front yard.

  • If the first arriving unit lacks a combustible gas meter, they must advise dispatch. This prompts the first unit with a meter to have their officer report to the Incident Commander (IC) with the device.

• Metering Equipment and Thresholds:

  • 4-Gas Meter: Used for evacuation decisions based on Lower Explosive Limit (LEL) readings.

  • Sniffer: Used to pinpoint the specific source of the leak.

  • LEL Alarms or Strong Odor: Immediately exit the building unless rescue is necessary.

• Rescue Specifics:

  • If making a rescue, personnel must “go on air” (use SCBA breathing air).

  • Critical Warning: Do not ventilate the building during the rescue. Ventilation may lower the gas concentration into the explosive range while rescuers are inside.

  • If the patient is difficult to access or conditions seem unsafe, exit the building immediately.

• Evacuation of Adjoining Structures: For row homes, evacuate three ($3$) houses in each direction.

• Water Supply: Be proactive by establishing water sources and laying hose lines outside of the designated collapse area.

Natural Gas Shutoff and Ventilation Procedures

Fire Scenarios: If fire is present, shut off the gas before attempting to extinguish the fire, unless an immediate life danger exists directly next to the fire.

• Isolation strategy: Always attempt to isolate the leak by shutting down only the affected appliance or line if possible.

• Gas Shutoff Priority Hierarchy:

  1. Appliance quarter-turn valve.

  2. Meter quarter-turn valve.

  3. Curb valve.

  4. Street valve.

• Reactivation Restriction: Never turn a gas valve back on once it has been cut off.

• Ventilation Strategy:

  • Ventilate from the top down after the gas is successfully turned off.

  • Ensure all ignition sources are prevented during ventilation.

  • Natural ventilation is preferred; breaking glass is usually unnecessary. If manual ventilation is required, use Positive Pressure Ventilation (PPV) (“push”).

• Notifications and Safety:

  • Notify BGE (Baltimore Gas and Electric).

  • Use metering as the only definitive way to determine if an exposed structure is safe.

  • Remove all unnecessary personnel from the area; restrict the gas area to fire personnel in full turnout gear and SCBA.

  • Eliminate all ignition sources in hot and warm zones, including vehicle traffic, power equipment, and electrical or phone services.

Natural Gas Leak Outside a Structure

• Scene Control: OIC establishes control, isolates, denies entry, and evacuates the immediate area.

• Positioning: The first arriving engine positions at a minimum of $300\,\text{feet}$ from the leak. All other equipment stages one block as above.

• Plastic Gas Lines Warning: Do not attempt to stop the flow of gas from plastic gas lines. Gas flowing through plastic creates static electricity, which can lead to ignition.

• Structural Safety: If gas enters a structure, the incident should be upgraded (fill out the fire box) and handled according to the “Inside a Structure” protocols.

• Gas Cloud Dissipation: If life or property is at risk, consider using water fog lines to dissipate the gas cloud.

• High-Pressure Leaks: For leaks blowing upward at high pressure, notify Air Traffic Control to control the airspace above the scene (e.g., to prevent media helicopters from entering the plume).

Propane Gas Leak Inside a Structure

• Response Standards: Similar to natural gas, positioning is at a minimum of $300\,\text{feet}$, evacuation is required, and full PPE/SCBA is mandatory for entry crews.

• Metering and Rescue: Use a 4-Gas Meter for evacuation and a Sniffer for localization. If LEL alarms or strong odors are present, exit the building unless rescue is required. Do not ventilate during rescue to avoid the explosive range.

• Ventilation Difference: Because propane is heavier than air, once the gas is turned off, ventilation must be conducted from the bottom up.

• Shutoff Priority: Follow the same hierarchy (appliance, meter, curb, street). Use natural ventilation or PPV/Push if necessary.

• Propane Notifications: Notify the local propane supplier. The supplier's name and contact number should be located on the propane tank.

• Safe Zones: Restrict the area and eliminate all ignition sources (traffic, electrical, phone) in the hot and warm zones.

Propane Gas Leak Outside a Structure

• Positioning: According to the transcript (“2st” arriving engine), the unit will position a minimum of $300\,\text{feet}$ from the leak.

• Fire Suppression and Cooling:

  • Shut off gas before extinguishing fires.

  • Water Requirements: A propane tank requires a $500\,\text{gpm}$ water spray per direct flame impingement.

  • Use an unmanned monitor line for this cooling stream.

• Emergent Vent Flame: Do not extinguish the flame emanating from the emergency vent of the tank.

• Structural Exposure: Use metering to verify if adjacent structures are safe. If gas enters a structure, follow the propane “Inside a Structure” protocols.

• Gas Cloud Dissipation: Use water fog lines if life or property is at risk to dissipate the gas cloud.