Halocarbons are organic chemical compounds containing one or more atoms of carbon and hydrogen plus one or more atoms of fluorine, bromine, chlorine, or iodine which may be present in various combinations in the compound.

You may be more familiar with their brand or trademark names such as: Freon(s), Gentron, Genesolv D, Frigen, AFFF, or carbon tetrachloride. As Enginemen, we work with these refrigerants, solvents, and fire extinguishing com-pounds regularly aboard ship. The extended and routine usage of halocarbons in the military and civilian environments (e.g., home/car air conditioners) has led us to a false sense of security which makes us forget the inherent poisonous nature of halocarbons, particularly when used in high concentrations in enclosed or confined spaces.

Warnings, hazards, and cautions in technical and training publications are usually benign. The labeling of containers and storage areas are consistently inadequate. The procedures for the disposal of halocarbon waste are not well known nor are they followed. Most people do not know the physiological effects of high concentrations of halocarbons on humans or the recommended first aid by both medical and non-medical personnel.

All Enginemen who handle or use halocarbons must be aware of the hazardous properties of halocarbons. The greatest hazards have been associated with Freon 113 refrigerant and Genetron 113 (a fluorocarbon compound), with the chemical name of TRICHLOROTRIFLUOROETHANE, which is used in large quantities for cleaning refrigeration, hydraulic, air and oxygen systems, and as a solvent for removing oil and grease from machinery. Trichlorotrifluoroethane is a heavy, colorless liquid at room temperature, and has an odor similar to dryclean-ing fluid. Because of its low boiling-point it evaporates rapidly at room temperature. Its vapor is several times heavier than air and tends to col-lect in low places.

Trichlorotrifluoroethane should always be treated as a toxic solvent. Exposure to it can cause headache, rapid heartbeat, light-headedness, and tingling of fingers or toes. Any of these symptoms is a warning to leave the area immediately. In higher concentrations the solvent has an anesthetic effect (causing uncoordination and stumbling); it can effect the heartbeat (causing irregular beats or even stoppage) and can cause tremors, convulsions, and DEATH. Refrigerant gases such as Freon 12 and 22 have properties similar to the ones described above except that they are practically odorless and can cause freeze burns.

During all primary maintenance or industrial uses of halocarbons such as flushing or recharging refrigeration or air conditioning systems, the following good engineering precautions are mandatory:

1. Strict compliance with NSTM gas-free Engineering directions for entry into enclosed or confined spaces, and close adherence to standard operating procedures for all halocarbon maintenance actions.

2. Tested and operational ventilation systems. Availability of portable equipment to provide in-take fromand exhaust to the atmosphere (not recirculation) sufficient to maintain halocarbon concentration at acceptable limits throughout the whole maintenance action. (Example: The limit for continuous exposure to the vapors of Freon 113 is 1000 parts of solvent per million parts of air. This limit will be reached by evaporation of approximately 100 milliliters (less than 1/2 cup) of solvent in a 10 10 10 ft. space). Local exhaust ventilation capable of maintaining a minimum capture velocity of 100 fpm over the face of the container or operation is normally required in order to maintain the vapor within acceptable limits. Note: Absolutely NO venting of halocarbons below decks shall be permitted.

3. Positive pressure emergency breathing devices with supplied air available in the space for instant donning and egress in the event of a halocarbon mishap.

4. Established two-way communications between the halocarbon pump at the bulk source and the equipment being filled, cleaned, or flushed. A backup sound powered system is recommended.

5. Verification of filling and flushing system integrity by leak testing (e.g., a pressure drop test) before halocarbon operations commence.

6. A minimum of two people should be stationed in the space, with a safety observer (tender) in the vicinity of the egress route if available. Rescue equipment (as necessary) to quickly remove personnel from the space in the event of an emergency. (Rescue personnel should also be equipped with protective clothing and positive pressure respiratory protection.)

7. A medical department representative, who is trained and knowledgeable in the physiological effects, prescribed first aid and emergency treat-ment methods for halocarbon mishaps, should be alerted to the maintenance action being performed and standing by for quick response.

8. An emergency eyewash/shower system in the immediate vicinity of all halocarbon operations should its use be required. Where a permanent system is not available, a portable system of 5-10 gallon capacity should suffice. Only potable water should be utilized for this purpose.

9. Ships emergency rescue teams (e.g., Flying Squads and repair parties) familiar with the hazards of halocarbons and trained in air-supplied respirator requirements when involved in halocarbon rescue operations.

10. The performance of hot work is prohibited from halocarbon work areas, due to the potential decomposition of halocarbons into more toxic chemicals.

As stated earlier, in high concentrations, halocarbons are toxic chemicals. Any handling or usage of these chemicals requires the following minimum personal protective measures:

1. Full-length face shield or chemical workers goggles

2. Apron or coveralls (both may be required)

3. Elbow length gloves

4. Boots or booties

5. Clothing and equipment must be im-pervious and resistant to halocarbons.

Note: Non-impervious clothing which becomes wet with halocarbons must be immediately removed and not reworn until all traces of the chemical are removed by cleaning.