User:Ruraldoctor

Oxidizers also known as oxidizing agents and oxidant are compounds that readily transfer oxygen that stimulates the combustion of other materials or corrosion of metal substances.

Example of Combustion:

Decomposition of Hydrogen peroxide

2 H2O2 → 2 H2O + O2

Example of Corrosion (Iron oxide) in Iron

2Fe(s) + O2(g) + H2O(l) ==>Fe(OH)2

Oxidising substances are categorised as Class 5, division 5.1 in the Australian Dangerous Goods Code. By definition, class 5.1 are substances that are not necessarily combustible themselves but causes or contribute to the combustion of other materials by yielding oxygen.

Oxidisers such as hydrogen peroxide, sodium hypochlorite and calcium hypochlorite are widely used in many areas, common uses forhydrogen peroxide, sodium and calcium hypochlorite include laboratory reagent, disinfectant and as bleaching agents. Hydrogen peroxide is also used in large scales as catalysts in the making of plastics in the polymer industry.

Oxidisers are divided into three packing groups, PG I, II and III mainly dependant on their level of hazard or potential risks. For most Oxidisers the packing group correlates with the concentrations, with the exception of weak oxidisers. Generally highly concentrated oxidisers are classified as PG I while moderate and low concentrated oxidisers are listed as PG II and PG III respectively.

PG I – This group of oxidisers possesses greatest hazard level. E.g. >60% conc. Hydrogen peroxides, perchloric acid.

PG II - These oxidisers possesses moderate hazard level. E.g. commercial hydrogen peroxides for bleaching purposes, dry pool chlorines as disinfectants and potassium permanganate.

PG III - Oxidisers in this group have minor hazard level. E.g. Ammonium nitrate as fertilisers.

Not all oxidisers are classified as oxidising substances. To identify if an oxidiser matches the criteria for the classification, the substance undergoes different tests depending on which state it is in according to the

The substance must be mixed with dry fibrous cellulose in ratios of 1:1 and 4:1. The burning characteristics of the mixture is then compared with the standard 3:7 mixture(by mass) of potassium bromate to cellulose, for burning times equal or less than the standard mixture the test substance must be then compared with PG I or II reference standards 3:2 and 2:3 mixture (by mass) of potassium bromated to cellulose. The test results are assessed on the average burn time in comparison to the reference mixtures and whether or not the mixture ignites. PG I – mixture of substance and cellulose in 4:1 or 1:1 ratio has a mean burning time of less than the standard 3:2 mixture of potassium bromate with cellulose. PG II – mixture of substance and cellulose in 4:1 or 1:1 ratio has a mean burning time of equal or less than the standard 2:3 mixture of potassium bromate with cellulose. PG III - mixture of substance and cellulose in 4:1 or 1:1 ratio has a mean burning time of equal or less than the standard 3:7 mixture of potassium bromate with cellulose. Not classified in Division 5.1 – mixture of substance and cellulose in 4:1 or 1:1 ratio has a mean burning time of greater than 3:7 mixture of potassium bromate with cellulose and/or does not ignite and burn.

Classification of test results are assessed on the mean time taken to rise a pressure of 690KPa to 2070KPa and whether or not the mixture of 1:1 substance to cellulose ignites spontaneously PG I – test 1:1 mixture spontaneously ignites, has a mean pressure rise time less than the standard 1:1 50% perchloric acid and cellulose mixture PG II – test 1:1 mixture has a mean pressure rise time less than or equal to the standard 1:1 40% aqueous sodium chlorate solution and cellulose mixture, with criteria that does not meet to that of PG I. PG III – test 1:1 mixture has a mean pressure rise time less than or equal to the 1:1 65% aqueous nitric acid and cellulose with criteria for PG I and PG II does not met. Not Division 5.1 – mixture which in 1:1 ratio with cellulose that show a pressure rise of less than 2070KPa and/or have a mean pressure rise time greater than that of 1:1 65% aqueous nitric acid and cellulose mixture.

Even though oxidisers are not liable to self-combustion, the primary risk is in its ability to provide and act as an oxygen source that enable the combustion of other materials (organic substance including flammable liquid and solids such as petrol) allowing them to burn with ease and with greater intensity. In general, oxidisers also possess corrosion hazards - namely perchloric acid, as the hazards associated with its use are highly severe.

When dealing with oxidising agents (ADG class 5.1 or subsidiary Risk 5.1) key factors should be aware: - READ and understand MSDS and container labels before using chemicals - Wear proper personal protective equipment. e.g. gloves, goggles and labcoat, faceshield if nessessary. - Keep oxidisers away from combustible substances. E.g. Sulfer and powdered metals such as magnesium. - Avoid contact with heat and ignition sources. - Ensure the temperature of the oxidiser does not approach within 15 degrees celcius of the decomposition temperature.

Factors to consider for storage: - Materials should be place on a reachable shelf height to allow ease of access and should be isolated from other substances. Shelves should be made of ceramic as spillage could cause wood to ignite. - The packages should be tightly sealed in a tinted bottle to avoid direct sunlight and heat. - A minimum distance of 5m apart from combustible material containers must be ensured, as it would lead to possible fire hazard. - Liquids must not be stored above oxidisers as it may cause fire hazard. - Ensure good housekeeping by cleaning surface regularly to avoid accumulation of dust particles. Spills should be cleaned up immediately and wastes should be disposed properly in labelled containers to avoid potential reaction of wastes.

Class B fire extinguishers are suitable for most fire caused by oxidisers. MSDS will provide sufficient information regarding different choices of fire extinguishers and fire fighting methods. Identify exits and water sources prior to handling of the oxidiser and evacuate area for large fire hazards and report to emergency service.

Oxidisers are irritating to skin, respiratory organs and eyes. For skin and eye contact, rinse immediately with running water for at least 20minutes before contact with doctors/first aid officer. If vapours are inhaled, leave area and get some fresh air and seek medical attention. For spillage on clothing, remove immediately and rinse with water to decontaminate.

http://safety.science.tamu.edu/oxidizers.html http://www.ntc.gov.au/filemedia/Publications/ADG7_Volume_1_Part_2.pdf

http://www.laynesafety.com/dmdocuments/manuals/australia/b5aus_a4.pdf

http://www.workcover.nsw.gov.au/formspublications/publications/pages/storageandhandlingofdangerousgoodscodeofpractice.aspx

• "STORAGE AND HANDLING OF DANGEROUS GOODS"