10.1 Pressurized Containers and Chlorine Kits A/B/C

10.1 Pressurized Containers and Chlorine Kits A/B/C

Quick Answer: A leaking chlorine pressure container is not a 55-gallon drum problem. Match the Chlorine Institute kit to the specification: Kit A = standard DOT 3A480 and 3AA480 100- and 150-pound cylinders (valve and sidewall). Kit B = standard DOT 106A500X ton container (valves, fusible plugs, sidewall) — not for a liquid-full ton; rotate the leak to the gas (top) position when you can. Kit C = DOT 105J500W chlorine tank cars, DOT MC331 chlorine cargo tanks, and DOT 51 portable tanks in chlorine service (angle valves, pressure-relief device, pressure plate). Find leaks with aqua-ammonia vapor, not a liquid stream. 49 CFR 173.3(e) can allow one-time, one-way movement of a Kit A or Kit B valve/fusible-plug repair — not the sidewall patch. PPE is a decision, not one mandated suit.

Chapter 9 taught atmospheric containment: wooden plugs, drum patches, salvage drums. NFPA 470 (2022) 11.4.3.2 still covers controlling container leaks, but the energy in a chlorine cylinder, ton, tank car, or MC331 is stored pressure plus a toxic liquefied gas. Texas A&M Engineering Extension Service (TEEX) and the Center for Domestic Preparedness (CDP) list A, B, and C Chlorine Kits as technician skills for that reason. Improvised wood on a chlorine valve is how you get a bigger hole and a second victim.

Why chlorine is a pressure-kit chemical, not a wedge chemical

Chlorine (UN 1017) is a green-yellow toxic gas shipped as a liquefied compressed gas. Emergency Response Guidebook (ERG) 2024 Guide 124 is the initial-isolation picture. Vapor density is greater than 1 (about 2.5 relative to air) — it sinks and fills basements, ditches, and pump pits. With moisture it is corrosive (hydrochloric and hypochlorous acids on wet tissue, metals, and suit visors). Liquid flashing to gas expands on the order of 460:1. A liquid leak is therefore a volume-of-cloud problem, not just a wet-floor problem. National Institute for Occupational Safety and Health (NIOSH) immediately dangerous to life or health (IDLH) for chlorine is 10 ppm. That is why the walk-up is atmosphere-supplying respiratory protection, not an air-purifying cartridge you hope is listed.

The kits are chlorine-service specific. The Chlorine Institute designs them for chlorine containers, not for anhydrous ammonia, sulfur dioxide improvisation in the field, or “any green cylinder.” If the specification plate is not a chlorine 3A/3AA, 106A500X, 105J500W, MC331 chlorine cargo tank, or DOT 51 chlorine portable tank, stop and get the right procedure. CHLOREP, CHEMTREC, and the supplier exist because this is a specialty leak.

Match the kit to the container — this is the exam table

Memory hook: A = alone cylinder you can two-person carry. B = big ton (a short ton of product). C = car / cargo / container (rail car, highway 331, portable tank).

Current instruction booklets matter more than academy folklore. IB/B Edition 12 Revision 2 (January 2026) is the live Kit B booklet; follow that booklet’s device sequence and torque language. Do not invent foot-pound numbers on the written exam or on the prop. Use the kit wrenches that came in the box. Indian Springs manufactures the Chlorine Institute kits to CI design specifications; Midland, Indian Springs emergency-response, and Kelso tank-car kits are versatile alternatives the Institute itself notes when a C-kit is not on scene — they are not an excuse to grab a hardware-store cap.

A Chlorine Institute Recovery Vessel is a different object: a salvage cylinder built to completely contain a leaking 3A480 / 3AA480 100- or 150-pound cylinder. If the leak will not take Kit A, or the cylinder is too damaged to trust, the recovery vessel is the containment, not a bigger wooden plug.

Position the leak in the gas space; do not kit a liquid-full ton

Ton containers have two valves on one head. With the valves vertical, the upper valve is the gas eduction and the lower valve is liquid. Six fusible plugs (three per head, about 120° apart) protect against heat, not overfill. Always — when you can safely maneuver the vessel — rotate so the leaking valve or fusible plug is on top, in the gas position. You want gas, not a liquid stream that flashes 460 times its volume. Chock the ton so it cannot roll while you apply the hood.

Kit B is not designed for liquid-full ton containers. Applying a capping hood onto a vessel with no vapor space can over-pressure the hood and the remaining wall. Reduce product and relieve pressure first — which often means the supplier, a transfer plan (Section 10.3), or waiting, not a hero hood. Kit A instructional practice makes the same liquid-full warning for cylinders. Kit C booklets likewise warn against liquid-full tank cars and cargo tanks. If the wreck left the tank hydrostatically full, the IAP is not “clamp it anyway.”

A sidewall leak: roll the container until the hole is uppermost (vapor) before the patch goes on, if the remaining product and stability allow it. A hole under the liquid line is a fountain.

Find the leak with vapor, not a squirt

Chlorine plus ammonia vapor makes a dense white cloud (ammonium chloride mist). The kit and water-treatment practice is 5–30% aqua ammonia (ammonium hydroxide) in a squeeze bottle, dip tube cut short so you expel vapor, not liquid. Direct the vapors at packing, threads, fusible metal, and hood seats. Do not spray liquid ammonia onto connections — you add corrosion and a wet mess on the very surfaces you need to seal. Household ~5% ammonia may be too weak for a small leak. This is a detector, not a neutralizer and not a foam blanket.

Work in pairs. Chlorine Institute kit videos and booklets are blunt: trained, protected people, never alone. The backup team (Section 10.4) is already dressed if the entry is in IDLH vapor.

PPE is a decision, not a poster

Chlorine is a toxic gas that can be IDLH in a small room at a modest leak, sinks, and is corrosive with moisture. Typical technician pictures:

• Unknown concentration, indoor leak, liquid spray, or you will work at the valve with your face in the plume: Level A (totally encapsulating vapor-protective suit) with positive-pressure SCBA (or SAR with escape SCBA) is the conservative skin-and-respiratory answer. Time in Level A is short (Section 10.4 and Chapter 6).
• Measured concentration, outdoor dissipating leak, splash not expected, AHJ risk assessment documented: Level B splash clothing with the same atmosphere-supplying respirator may be justified. Level A and Level B share the respirator; they do not share the suit.
• Air-purifying respirators are not the default for a leaking pressure container of chlorine. IDLH, unknown, and oxygen-deficient pits take SCBA.

Occupational Safety and Health Administration (OSHA) 1910.120(q)(6)(iii)(D) and (F) still limit you to the PPE and resources the unit actually has. No kit, no encapsulating suit, no trained pair — then the legal tactic is isolation, evacuation, and a request for a CHLOREP-capable team, not a structural firefighter in a wet hood standing over a 150-pound cylinder.

49 CFR 173.3(e) is a narrow highway exception, not a skill-lane shortcut

Pipeline and Hazardous Materials Safety Administration (PHMSA) 49 CFR 173.3(e) (current eCFR) allows trained personnel to temporarily repair:

1. A DOT 3A480 or 3AA480 cylinder of chlorine or sulfur dioxide that leaked at a valve or fusible plug, using Kit A — except Device 8 (sidewall).
2. A DOT 106A500 multi-unit tank car tank of chlorine or sulfur dioxide that leaked at a valve or fusible plug, using Kit B — except Device 9 (sidewall).

The repaired package may move one time, one way, by private or contract carrier, from discovery to a proper facility for discharge and examination. Personnel training must include kit use, respiratory and other safety equipment, and properties of chlorine and sulfur dioxide. The package must be blocked and braced. That is not “drive it to the next county with a sidewall patch and call it legal,” and it is not a Kit C tank-car rule.

Sequence on the prop (TEEX / CDP / TCFP)

Identify the spec and the product. Dress. Control ignition only if a flammable mix is also in play (chlorine itself is not a fuel, but it supports combustion of some materials and will wreck lungs either way). Approach upwind / uphill of the low-lying cloud. Try the simple mechanical step first when the booklet allows it (close the stem, snug a packing nut, snug a fusible plug without over-torquing). If it still leaks, apply the matching hood or patch. Ammonia-vapor test. Chock. Report. Plan recovery vessel, transfer, or 173.3(e) movement only after the leak is actually in a device the regulation recognizes.

Scenario: plant cylinder versus a rolled ton

Scene 1. A 150-pound chlorine cylinder at a water plant is weeping at the valve inlet threads. That is Kit A, Device-1-type valve hood territory after you confirm the stem is closed — not Kit B, not a drum clamp, not a Level D walk-up. If the same cylinder is holed in the sidewall, Kit A’s sidewall device can contain it for the emergency, but 173.3(e) will not let you highway-ship that Device 8 repair; think recovery vessel or supplier.

Scene 2. A 106A500X ton is on its side after a forklift strike. Lower valve is dumping liquid. Do not hood the lower valve in place. Chock and rotate until that valve (or the leaking fusible plug) is up in gas, confirm the vessel is not liquid-full, then apply Kit B. If you cannot rotate it and cannot reduce liquid, you have a transfer / supplier problem, not a “force the hood” problem.