Editorial Note on Part 173
Editorial Note: Nomenclature changes to part 173 appear at 70 FR 56098, Sept. 23, 2005.

§ 173.309 Fire extinguishers. This section applies to portable fire extinguishers for manual handling and operation, fire extinguishers for installation in aircraft, fire extinguishers for installation as part of a fire suppression system, and large fire extinguishers. Fire extinguishers for installation as part of a fire suppression system include cylinders charged with either a compressed gas and an extinguishing agent or a gas which comprises the sole fire extinguishing agent in the system. A fire extinguisher does not include cylinders pressurized with a gas for purposes of expelling a separately stored extinguishing agent in the fire suppression system. Large fire extinguishers include fire extinguishers mounted on wheels for manual handling; fire extinguishing equipment or machinery mounted on wheels or wheeled platforms or units transported similar to (small) trailers; and fire extinguishers composed of a non-rollable pressure drum and equipment, and handled, for example, by fork lift or crane when loaded or unloaded. Cylinders filled with a compressed gas whose purpose is to expel a separately stored extinguishing agent may not be transported under this section when offered for transportation or transported apart from a suppression system. ( a ) Specification 3A, 3AA, 3E, 3AL, 4B, 4BA, 4B240ET or 4BW (§§ 178.36, 178.37, 178.42, 178.46, 178.50, 178.51, 178.55 and 178.61 of this subchapter) cylinders are authorized for manufacture and use as fire extinguishers under the following conditions: ( 1 ) Extinguishing agents must be nonflammable, non-poisonous, non-corrosive, and commercially free from corroding components;
( 2 ) Each fire extinguisher must be charged with a nonflammable, non-poisonous, dry gas that has a dew-point at or below minus 46.7 °C (minus 52 °F) at 101 kPa (1 atmosphere) and is free of corroding components, to not more than the service pressure of the cylinder;
( 3 ) A fire extinguisher may not contain more than 30% carbon dioxide by volume or any other corrosive extinguishing agent; and
( 4 ) Each fire extinguisher must be protected externally by suitable corrosion-resisting coating.
( 5 ) Specification 3E and 4BA cylinders must be packed in strong non-bulk outer packagings. The outside of the combination packaging must be marked with an indication that the inner packagings conform to the prescribed specifications.
( b ) Specification 2P or 2Q (§§ 178.33 and 178.33a of this subchapter) inner non-refillable metal packagings are authorized as fire extinguishers subject to the following conditions: ( 1 ) Extinguishing agents must be nonflammable, non-poisonous, and non-corrosive as defined in this subchapter;
( 2 ) The liquid portion of the gas plus any additional liquid or solid may not completely fill the packaging at 55 °C (130 °F);
( 3 ) Pressure in the packaging must not exceed 1250 kPa (181 psig) at 55 °C (130 °F). If the pressure exceeds 920 kPa (141 psig) at 55 °C (130 °F), but does not exceed 1100 kPa (160 psig) at 55 °C (130 °F), a specification DOT 2P inner metal packaging must be used; if the pressure exceeds 1100 kPa (160 psig) at 55 °C (130 °F), a specification DOT 2Q inner metal packaging must be used. The metal packaging must be capable of withstanding, without bursting, a pressure of one and one-half times the equilibrium pressure of the contents at 55 °C (130 °F);
( 4 ) Each completed inner packaging filled for shipment must have been heated until the pressure in the container is equivalent to the equilibrium pressure of the contents at 55 °C (130 °F) without evidence of leakage, distortion, or other defect; and
( 5 ) Specification 2P and 2Q cylinders must be packed in strong non-bulk outer packagings. The outside of the combination packaging must be marked with an indication that the inner packagings conform to the prescribed specifications.
( c ) Non-specification cylinders are authorized as fire extinguishers subject to the following conditions: ( 1 ) Extinguishing agents must be nonflammable, non-poisonous, and non-corrosive as defined in this subchapter;
( 2 ) The internal volume of each cylinder may not exceed 18 L (1,100 cubic inches). For fire extinguishers not exceeding 900 mL (55 cubic inches) capacity, the liquid portion of the gas plus any additional liquid or solid must not completely fill the container at 55 °C (130 °F). Fire extinguishers exceeding 900 mL (55 cubic inches) capacity may not contain any liquefied compressed gas;
( 3 ) Each fire extinguisher manufactured on and after January 1, 1976, must be designed and fabricated with a burst pressure of not less than six times its charged pressure at 21 °C (70 °F) when shipped;
( 4 ) Each fire extinguisher must be tested, without evidence of failure or damage, to at least three times its charged pressure at 21 °C (70 °F) but not less than 825 kPa (120 psig) before initial shipment, and must be marked to indicate the year of the test (within 90 days of the actual date of the original test) and with the words “MEETS DOT REQUIREMENTS.” This marking is considered a certification that the fire extinguisher is manufactured in accordance with the requirements of this section. The words “This extinguisher meets all requirements of 49 CFR 173.306” may be displayed on fire extinguishers manufactured prior to January 1, 1976;
( 5 ) Each non-specification fire extinguisher must be packaged as an inner packaging within a combination outer packaging. Examples of acceptable outer packagings for non-specification fire extinguishers include large cartons, racks, cages or other suitable enclosures; and
( 6 ) For any subsequent shipment, each fire extinguisher must be in compliance with the retest requirements of the Occupational Safety and Health Administration Regulations of the Department of Labor, 29 CFR 1910.157.
( d ) Limited quantities: Fire extinguishers otherwise conforming to paragraph (a), (b), or (c) of this section and are charged with a limited quantity of compressed gas to not more than 1660 kPa (241 psig) at 21 °C (70 °F) are excepted from shipping papers (except when offered for transportation by aircraft or vessel), labeling (except when offered for transportation by aircraft), placarding, the specification packaging requirements of this subchapter, and are eligible for the exceptions provided in § 173.156 when offered for transportation in accordance with this paragraph (d). Limited quantity shipments conforming to this paragraph are not subject to parts 174 and 177 of this subchapter when transported by highway or rail. In addition, limited quantity packages of fire extinguishers are subject to the following conditions, as applicable: ( 1 ) Extinguishing agents must be nonflammable, non-poisonous, and non-corrosive as defined in this subchapter; and
( 2 ) Packages must be marked as specified for limited quantities in § 172.315 of this subchapter.
( e ) Large fire extinguishers may be transported while unpackaged under the following conditions: ( 1 ) The requirements of § 173.24(b) are met;
( 2 ) The valves are protected in accordance with § 173.301b(c)(2)(i), (ii), (iii) or (v); and
( 3 ) Other equipment mounted on the fire extinguisher is protected to prevent accidental activation.
[78 FR 1116, Jan. 7, 2013, as amended at 80 FR 1162, Jan. 8, 2015; 80 FR 72927, Nov. 23, 2015; 85 FR 85419, Dec. 28, 2020]