With some farmer’s ready to take another cut of silage, we would like to remind our clients of the hazards involving ammonium nitrate fertiliser and silage gases.
Ammonium Nitrate
Ammonium nitrate is one of the most commonly used sources of artificial nitrogen in the UK.
Fertilisers that contain 28% or less nitrogen do not normally present an explosion hazard and therefore, ammonium nitrate-based fertilisers are usually divided into two groups:
Fertilisers that contain more than 28% nitrogen. Most of these are straight ammonium nitrate types, although they include a small number of compound fertilisers.
Fertilisers that contain 28% or less nitrogen. Compound fertilisers form the major proportion of this group. The straight nitrogen types are usually a mixture of ammonium nitrate with limestone or similar inert materials.
Ammonium nitrate will not explode during normal handling, but it can be detonated under heat, confinement, or severe shock. For example, in a fire, pools of molten ammonium nitrate may be formed and if the molten mass becomes confined (e.g. in drains, pipes, plant or machinery) it could explode, particularly if it becomes contaminated.
Storage areas
- Ammonium nitrate should normally be stored in single storey, dedicated, well-ventilated buildings that are constructed from materials that will not burn, such as concrete, bricks or steel, and have no internal drains.
- Storage should be away from possible sources of heat, fire or explosion, such as oil storage, gas pipelines, timber yards, flammable liquids, flammable solids and combustible materials including hay, straw and feedstuffs.
- Stores should be cleaned before they are used for storing ammonium nitrate.
Stacks
- Self-confinement of straight ammonium nitrate in large stacks can increase the risk of a detonation of the whole stack in a fire, so limit stacks to a maximum of 300 tonnes.
- Do not store ammonium nitrate that contains more than 28% nitrogen in the same stack as other products.
- Where a site contains 25 tonnes or more of dangerous substances, the Dangerous Substances (Notification and Marking of Sites) Regulations 1990 require the person in control of the site to notify the fire authority and enforcing authority.
For more information and source, see https://www.hse.gov.uk/pubns/indg230.pdf
Silage Gases
Various gases can be produced during the harvesting, filling, and the first 2 to 3 weeks of ensiling silage pits. Silage gases can also accumulate in feed rooms or livestock housing areas and can be fatal to both humans and animals.
Nitrogen Dioxide
Nitrogen dioxide (NO2) gas is extremely dangerous. It is heavier than air and characterized by an orange to yellowish-brown colour and has a similar smell to laundry bleach.
To help ensure safety, allow any orange to yellowish-brown gasses to fully dissipate before approaching the silage.
The highest levels of NO2 are usually present during the first 24 to 72 hours after the forage is put into the silo, but dangerous levels can persist for up to 3 weeks.
NO2 gasses are usually associated with conventional, top-unloading silos but are still a risk for other ensiling structures such as bunkers, bags, or piles.
Depending on the NO2 concentration, the presence of this gas might be recognized by a burning sensation in the nose, throat, and/or chest. Exposure to high concentrations of NO2 can cause respiratory issues or death quickly without allowing time to detect respiratory symptoms.
Move into the fresh air at once if you should experience even slight throat irritation or cough around a silage structure. See your doctor immediately if you suspect that you have been exposed to NO2.
Carbon Dioxide
Carbon dioxide (CO2) is an odourless, colourless, and tasteless gas that is heavier than air. It is particularly hazardous in sealed tower silos, where CO2 replaces oxygen in the confined headspace. In bunkers, bags, or piles, CO2 is often seen as a shimmering wave rolling down the silage and across the ground.
The contained atmosphere in a tower silo can be almost entirely CO2 and survival in such an environment is entirely dependent on a safe external air supply.
In conventional, top-unloading silos, CO2 can accumulate to dangerous concentrations by draining into low points on the silage surface.
Remember
- Stay clear of silos and piles for 2 to 3 weeks after filling.
- Ventilate feed rooms with open windows and fans during the danger period.
- Keep the doors between the silo feed room and livestock housing area closed tightly.
- If it is necessary to enter a silo after filling, do so as soon as the last load is off the truck or wagon. Do not wait until the next day and have the forage blower running while you are in the silo.
- If you must enter or open a silo within 3 weeks after filling:
- Ventilate the silo by running the forage blower for 15 to 20 minutes before entering with the door closest to the top of the silo open.
- Wear an approved, self-contained breathing apparatus and have a connection to a person outside the silo.
- When opening up a bag, pile, or bunker, allow any gases to fully dissipate overnight before allowing the feed team to begin removing silage.
- Watch for Orange or Brown Gas – this is likely to be the very dangerous Nitrogen dioxide (NO2).
- Take care when opening new season silages, especially in enclosed environments.
Image: @anthonygibbon8
