The GRDC Grain Storage Extension Team are often asked what tools and equipment aid grain storage management and where they can be sourced.
This catalogue is a reference of useful equipment with examples of where they can be sourced.
Dust exposure is a common but often overlooked safety risk in grain storage operations. Watch as Chris Warrick and Ben White from the GRDC Grain Storage Extension Team discuss the importance of choosing the right dust masks, respirators, and eye protection when working around grain storages, silos, and sheds. Learn when to use P2 and P3 dust masks, the benefits of full-face respirators, and how sealed safety goggles help protect against airborne dust during grain handling, storage cleaning, and compressed air use.
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Appropriate Personal Protective Equipment (PPE) is essential for health and safety when fumigating with phosphine.
The phosphine label mandates the use of a full-face respirator with a combination particulate (P1) and phosphine gas cartridge filter along with elbow-length rubber gloves to comply with label requirements.
As silos age, growers face a crucial decision: repair, retrofit, or replace. The first step is always safety. Grain Storage Specialist Chris Warrick advises that growers begin by checking whether the silo is structurally sound. Cracked or tilted bases, rust on critical joints, or weakened bolts and sheets can all compromise safety and increase the risk of collapse. Faulty hatches, ladders, and access points also need to be addressed to protect workers.
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Grain Storage Specialist Alex Conway guides us through purchasing the correct mask for handling phosphine.
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Grain Storage Specialist Alex Conway explains the various types of phosphine monitoring equipment. Types covered include high-range for fumigation, low-range for safety or clearance and real-time monitors.
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Recent reports indicate an increasing number of trucks are being rejected at delivery for excess phosphine. The rejections fall into one of two categories: high-level phosphine, where phosphine has been misapplied and put people in danger, and low-level phosphine, where the grower’s fumigation practices need tweaking to vent gas to a lower level.
Attempted fumigations just prior to, or even during, transport are thought to be the leading cause of the high phosphine readings at delivery sites. Misuse of phosphine, including any off-label practices, places operators, truck drivers, delivery site staff and, potentially, the general public in danger. Perpetrators in this category can expect to deal with the authorities and the consequences, which often involve quarantining the truck for several days until the load is vented to a safe level for off-loading.
Low-level phosphine rejections are the ones on the rise, according to the bulk handler, and there are a few contributing factors:
Testing for phosphine residue at delivery ensures operators are not exposed to harmful levels of the gas while handling the grain. Confusion on what is a safe clearance level for phosphine has led the bulk handler to use a limit of 0.3ppm taken via a grain spear sample.
The safety limit of 0.3ppm is supposed to be measured via the time-weighted average in the enclosure and work area, not the grain bulk itself as the bulk handler is doing. Further research is required to develop a sampling method and gas limit to ensure operator safety, without unnecessarily penalising operators with small amounts of residual gas that does not pose a health and safety risk.
Gas concentrations found within a grain stack are significantly higher compared to the surface of the stack, let alone the air around it that operators are breathing.
Following a fumigation with phosphine, the label directs venting either with aeration fans operated for two hours on and two hours off for not less than one day, or not less than five days without fans. Research has found that this venting period may not remove gas levels below 0.3ppm when sampled with a grain spear, so if a bulk handler is requiring this clearance level, a phosphine meter is the surest way to know when venting is complete.
It is worth noting that most phosphine meters are designed to measure either high range for fumigation gas levels or low range for clearance or safety. When purchasing a phosphine meter for checking venting progress, ensure the measuring resolution is accurate at low range to measure 0.3ppm.
There are multiple sources of phosphine meters in Australia; what’s important is checking the supplier guarantees quality and accuracy for low level readings. Two well-known suppliers in the eastern states are Canary Company, which sells the Silo Safe, and Graintec Scientific, which sells the Drager Pac 7000.
Handy optional extras with phosphine meters include a cradle for the Drager models to connect to a gas line or spear, the spear itself and pumps, either external or built-in to draw the gas to the meter.
A low-level phosphine meter is the surest way to know if grain has been adequately vented to the delivery requirements. Photo: Chris Warrick
For reliable clearance measurements, turn aeration fans off for at least 12 hours and take readings before out-loading grain from the storage.
Research has found that phosphine venting can take longer if the exposure period was extended, if the grain temperature was cold, or if the storage bulk was large (a flat-bottom silo greater than 1000 tonnes).
To ensure control of all life stages of insect pests, fumigation exposure periods must be long enough to allow the insects to continue developing to an active life stage to take up the gas; over 25°C takes seven days; between 15 to 25°C takes 10 days. Some operators choose to extend the fumigation exposure period to ensure gas concentrations reach the required 360ppm in all areas of the storage for the full seven to 10 days. What must be understood is that extending the exposure period allows more time for the grain to absorb the gas and, therefore, will also take longer to desorb during venting.
Cold grain has also been found to desorb phosphine slower than warm grain, so storages that have been under aeration cooling may take longer to vent below 0.3ppm than the one day directed by the label.
For obvious reasons, large storages can also take longer to vent given the distance gas has to travel through the grain before escaping.
Fumigation in grain bags has been proven possible. Phosphine is inserted into pipes placed every seven metres along the sealed bag for 10 days. However, venting can be the most challenging component to this fumigation process.
A large-capacity fan can be connected to the starting end of the bag and, with the other end of the bag propped open, gas can be sucked out in two or more days. If power is not available, recent research has found that passive venting is possible using 50-millimetre fumigation pipes, where the phosphine can be removed and caps left off – but expect it to take two weeks or more to vent below 0.3ppm.
GRDC Code PRB2011-001SAX
What’s the most important component to on-farm grain storage? Chris Warrick argues that it’s safety.
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The rescue unit is the first of its kind in Canada. Previously, units had been rented from the United States for demonstrations. It was designed and manufactured by Prairie Agricultural Machinery Institute in Humboldt.
The total time required for effective fumigation ranges from 10–17 days, accounting for the minimum exposure period, ventilation and withholding period. This highlights the importance of monitoring grain regularly and at least 17 days before out-loading to allow sufficient time to fumigate if required.
When determining how much phosphine to apply, it is important to treat the entire storage volume, regardless of how much grain is contained inside. For example, a 100 tonne silo full of grain requires 200 phosphine tablets. If that same 100t silo is only half full of grain, it still requires 200 phosphine tablets for effective fumigation.
Phosphine is a highly toxic gas with potentially fatal consequences if handled incorrectly. As a minimum requirement, the label directs the use of cotton overalls buttoned at the neck and wrist, eye protection, elbow-length PVC gloves and a breathing respirator with combined dust and gas cartridge.
Arrange the tablets where as much surface area as possible is exposed to air, so the gas can disperse freely throughout the grain stack. Spread phosphine tablets evenly across trays before hanging them in the head space or placing them level on the grain surface inside a gas-tight, sealed silo. Hang bag chains in the head space or roll out flat on the top of the grain so air can freely pass around them as the gas dissipates. Bottom-application facilities must have a passive or active air circulation system to carry the phosphine gas out of the confined space as it evolves. Without air movement, phosphine can reach explosive levels if left to evolve in a confined space.
To control pests at all life stages and prevent insect resistance, phosphine gas concentration needs to reach 300 parts per million (ppm) for seven days (when grain is above 25°C) or 200ppm for 10 days (between 15–25°C). Insect activity is slower in cooler grain temperatures so require longer exposer to the gas to receive a lethal dose.
Table 1 – Application rates for phosphine tablets in storage
Following fumigation, ventilate silos so grain can be delivered free from harmful gas residues. With tablet residue or bag chains removed, leave silos open for no less than five days, or no less than one day with aeration fans
operating. The final step is to hold grain for a further two days after ventilation before using for human consumption or stockfeed
Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Grains Research and Development Corporation. No person should act on the basis of the contents of this publication without first obtaining specific, independent professional advice. The Corporation and contributors to this Fact Sheet may identify products by proprietary or trade names to help readers identify particular types of products. We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred to. The GRDC will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication.
CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USE
Any research with unregistered pesticides or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the authors’ organisations. All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region. Copyright © All material published in this Fact Sheet is copyright protected and may not be reproduced in any form without written permission from the GRDC.
