Phosphine fumigation
Phosphine fumigants are widely used on farms to control insect infestation in many different stored grains and to control rodents and rabbits. Phosphine gas is the by-product of the action of moisture on metal phosphide tablets.
Inhalation of phosphine gas
Respiratory protection
Flammability
Safe practices
Inhalation of phosphine gas
When phosphine gas is inhaled, it can react with moisture in the lungs to form phosphoric acid, which can be serious or fatal.
Inhalation of the gas may occur from:
- leakage from fumigated silos or stacks
- inappropriate fumigation practices
- sleeping in trucks which have had phosphine placed in the load
- fumigating in enclosed sheds
- entering or examining silos or stacks immediately after fumigation
- leaving tablets and/or canisters in inappropriate places (e.g. ute floor)
- cleaning and/or hosing out silos that have been used for fumigation when the product has not reacted completely
Symptoms of poisoning from inhalation can be:
- coughing
- chest tightness
- headache
- double vision
- nausea
- vomiting
Exposure may lead to:
- anaemia
- bronchitis
- diarrhoea
- visual, speech and motor disturbances
Phosphine gas has an odour of decaying fish. However do not rely on the odour of phosphine to determine whether the atmosphere is safe because the odour threshold for phosphine is above the exposure standard.
If the odour threshold for phosphine is detected, evacuate the area immediately.
Respiratory protection
If a person has been overcome by phosphine gas, the rescuer must wear adequate respiratory protection to avoid also becoming a victim.
Respiratory protection includes:
- A full-face filter respirator or self-contained breathing apparatus must be worn if concentrations exceed 0.3ppm.
- The filter must be approved for phosphine and suitable for short-term exposure only (type B for inorganic gases).
- The filter should be immediately discarded and destroyed if there is any hint of phosphine odour inside the face-piece.
- Self-contained breathing apparatus should be used for operations such as breakdowns when longer exposures at higher concentrations may occur.
- Facial hair will prevent an adequate seal of the mask against the skin.
- A suggested life of 1 hour only for filters at usual exposure levels of operators in routine testing procedures is a recommended safeguard.
Flammability
Phosphine gas is flammable and may ignite when concentration in air exceeds 1.8%.
Materials added to tablets release carbon dioxide and ammonia with phosphine gas which are designed to prevent spontaneous ignition of the gas under normal circumstances.
Phosphine gas also reacts violently with acids and with compounds containing fluorine, chlorine, bromine and iodine.
Safe practices
Safe practices include:
- Always read the label before use and follow the manufacturer's instructions.
- Obtain a material safety data sheet (MSDS) from your chemical supplier which details information about treatment and symptoms of phosphine poisoning as well as chemical data.
- Wear correct respirator and protective clothing (see MSDS and label). Impervious gloves (e.g. PVC) should be worn when dispensing pellets by hand.
- Have an observer standing by who should have access to respiratory protection.
- Never use phosphine while grain is in transit.
- Monitor atmosphere around fumigation using hand pump and gas detector tube. The concentration should not be higher than 0.3ppm.
- Before moving grain after fumigation, make certain that all gas fumes have been dispersed. It is inadvisable to treat grain in airtight containers because of difficulties dispersing all gas fumes.
- Open phosphine containers in open air, not in shed or silo.
- Dispose of spent phosphine tablets correctly.
- Keep canisters locked away in a cool, dry place away from all habitation.
- Do not place tablets into tarped truck-loads of grain.
- Dispose surplus or part-filled containers in approved council land fills or according to the instructions on the label.
- Never increase dosage to have a 'better kill' of the insects.
- Always keep out of reach of children.
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