ODSs and Alternatives

Ozone Depleting Substances (ODSs)

The study of scientific proofs by an international institute revealed that the main cause of stratospheric ozone reduction and “ozone hole” is the chemicals in family of Halocarbons which synthesized by human beings for their industrial applications.

The Halocarbons is the so-called name of chemicals in type of Halogenated Hydrocarbons which consists of molecules of Halogens (Cl,Br,F) and Carbon (C). The important chemicals in this type are as follow;

Chlorofluorocarbons (CFCs)
CFCs are carbon compounds containing carbon, chlorine and fluorine. This chemical is used as refrigerant in air-conditioner to replace toxic refrigerants such as NH3 or SO2 .

Since CFCs have many positive properties such as non-flammable, non-erosive, less toxicity, non-explosive and hardly dissolved, they are used in a lot of applications i.e. medical activities, cleaning flux in electronic parts etc. CFCs used in industrial sector include;

CFC-11
Formula : CCl 3 F
Boiling point : 23.8 °c
Application : Refrigerant for a refrigerated room, a chiller etc.
Foam blowing agent in foam manufacturing industry and Aerosol propellant in canned spray industry

CFC-12
Formula : CCl 2 F 2
Boiling point : -30 °c
Application : Refrigerant for commercial refrigerator and mobile air-condition system, Foam blowing agent in foam manufacturing industry and Aerosol propellant in canned spray industry

CFC-113
Formula : CClF 2 CCl 2 F
Boiling point : 47.6 °c
Application : Cleaning flux in electronic parts

CFC-114
Formula : CClF 2 CClF 2
Boiling point : 3.8 °c
Application : Foam blowing agent in foam manufacturing industry and Aerosol propellant in canned spray industry

CFC-115
Formula : CClF 2 CF 3
Boiling point : -39.1 °c
Application : Cleaning flux in electronic parts and foam blowing agent in foam manufacturing industry

Halons
Halons are used as fire extinguishing agents due to its high efficiency, lightweight, less time in suppressing fire and no residues, however, this family of substance has 10 times more on ozone depleting potential (ODP) than CFCs. Types of Halons include;

Halon-1211
Formula : CF 2 BrCl
Boiling point : -3.88 °c
Application : Fire extinguishing agent for portable extinguishers

Halon-1301
Formula : CF 3 Br
Boiling point : -57.8 °c
Application : Fire extinguishing agent for fixed systems and also used in aviation industry


Carbon Tetrachloride (CTC)
CTC is a clear liquid, strong particular odor, non-dissolvable, non flammable and 5.3 times heavier than air. This substance is used for cleaning steels, production of sugar coated tablet and used as solvent in laboratory.

When heated to decomposition, CTC emits highly toxic fumes of phosgene and hydrogen chloride which may cause disease including damage to major human organs such as liver, kidney, heart, respiratory system, digestive system.

Methyl Chloroform
Methyl Chloroform has a chemical formula of CH 3 CCl 3 used as a solvent in shoe sole industry and cleaner in textiles industry.

Methyl Bromide
Methyl Bromide, an effective fumigant against a wide range of pests, is widely used in soil treatment, fumigation of commodities and fumigation of buildings and vehicles.

Methyl bromide is a non-flammable, colorless, and odorless gas, however, at high concentration, the odor of methyl bromide is like chloroform. With the boiling point of 3.6 degree Celsius, methyl bromide is a gas at normal atmosphere. It can therefore penetrate into soils and diffuse through commodity fumigation facilities, buildings and vehicles, reaching pests which would otherwise be difficult to eliminate. It is also effective in killing insects and other organisms at relatively low concentrations. Fumigation with methyl bromide also consumes less time than the other chemicals.

Each application of methyl bromide requires different level of concentration. In Thailand , Bromethane or 99.4% methyl bromide is used for fumigation of cut flowers and vegetables such as orchids and asparagus to eliminate rice thrips ( Thrips oryzae ). Since methyl bromide is a colorless and odorless gas, 2% chloropicrin is added for the safety purpose. When MB leak, users will be notified by the symptom of eye irritation which caused by chloropicrin. However, chloropicrin should not be used in monitoring the gas leakage because it can be absorbed by the commodities, therefore, when the eye irritation is noticed, the level of the gas leakage might be in harmful level.

Methyl bromide is a toxic chemical. Exposure to MB can cause acute and chronic toxicity, however it depends on exposure time and concentration. The symptoms of acute toxicity are headache, visual disturbances, nausea, and vomiting. Exposure to high concentration can cause extreme agitation, coma and convulsions. The symptoms of chronic toxicity are central nervous system and respiratory system failures, as well as specific and severe deleterious actions on the lungs, eyes, and skin. The toxicity will fade within a few days or many months from the day of exposure and the human body can normally recover by itself.