Food & Beverage

Food and beverage sites carry gas hazards that come from the process rather than from anything you would recognise as industrial chemistry. Ammonia because it is the most efficient refrigerant. Carbon dioxide because it carbonates, dispenses and stuns. Phosphine because grain has to be protected from insects. Methane and hydrogen sulphide because organic material decomposes.

Most of what follows comes from work our Technical Consultants have done on Australian sites.

Ammonia Refrigeration

Large scale cold storage and food processing runs on ammonia, and for good reasons. Anhydrous ammonia does not deplete ozone, unlike the refrigerants it replaced. It is considerably cheaper than synthetic alternatives. It is far less flammable than propane. And its thermodynamic properties make it genuinely efficient for meat and dairy processing at scale.

The trade-off is that it is toxic above 500 parts per million, at which point it causes lung damage and can kill. Documented leaks have occurred in bottling plants, frozen storage facilities and similar environments.

What is less widely understood is that ammonia is also flammable. Its explosive range runs from 16 percent as a lower explosive limit to 25 percent as an upper limit in air. Released into an enclosed plant room with an ignition source present, an ammonia leak becomes a fire and explosion risk as well as a toxic one.

There are two ways to cover it and the choice is not only technical.

Open path line of sight detection measures across a beam between a transmitter and a receiver, which suits monitoring an engine room or plant hall as a whole. Path lengths are available in bands from around 5 to 16 metres, 14 to 40 metres and 35 to 60 metres. The SafEye Quasar covers ammonia specifically in its 960 configuration.

Point detection places detectors where leaks actually start, at valves and flanges that fail under pressure, with a coverage radius of around 4 to 5 metres each.

Cost points in different directions. A point detector runs in the low thousands, an open path system considerably more, so a small plant room with three known leak sources is better served by point detection, while a large hall with an unpredictable leak location is better served by a beam. Where a plant has both, the sensible answer is usually both.

The environment is the other consideration. Low temperatures, condensation and frost are the normal operating condition in cold storage, and they are what causes detector failures rather than the ammonia. Secure mounting and an unobstructed beam path matter more here than on a warm site.

Refrigerating systems in Australia sit under AS/NZS 5149, which covers installation site requirements including detection and mechanical ventilation for machinery rooms. Workplace Health and Safety Queensland publishes specific guidance on ammonia based refrigeration systems that is worth reading regardless of which state you are in.

Carbon Dioxide In Beverage Dispensing

This is the application with the clearest Australian standard behind it, and the standard exists because somebody died.

AS 5034, Installation and use of inert gases for beverage dispensing, came into effect on 28 October 2005 following a coronial inquest into the death of a cellar worker. It was developed by a committee including the Australian Chamber of Commerce and Industry, state WorkCover authorities, industrial gas suppliers, insurers and breweries. It remains current, having been reconfirmed by Standards Australia in 2016.

The hazard is straightforward. Carbon dioxide is used to carbonate soft drinks, to pour beer and as a propellant to dispense drinks, often as a CO2 and nitrogen mix. Cylinders are commonly stored in cool rooms and cellars, which are frequently poorly ventilated and often meet the definition of a confined space. If a cylinder, regulator or line leaks, carbon dioxide displaces oxygen. It is colourless and odourless at normal temperature and pressure, so there is no warning without an instrument, and the effects of carbon dioxide exposure arrive well before the oxygen level falls far enough to asphyxiate.

What the standard sets out is specific. Carbon dioxide is to be maintained below 0.5 percent by volume and oxygen above 19.5 percent, in both naturally and non-naturally ventilated areas where people enter or work. Non-naturally ventilated storage areas that cannot meet the ventilation requirements require gas monitoring and ventilation devices. Since January 2012, compliance has applied to all non-naturally ventilated areas.

The requirement most often missed is the alarm arrangement. Audible and visual alarms must be present both inside the cellar or cool room and outside at the entry points, so that somebody about to walk in is warned before they do. A SON4 sounder beacon driven from the detector covers the outside position, and most venues need a monitor in both the cellar and the cool room even where the gas itself is stored outside.

One point worth being precise about. AS 5034 is an Australian Standard rather than legislation, and it has not been incorporated into work health and safety law, so it is not legally binding in its own right. The duty of care under WHS law is binding, and AS 5034 is the accepted means of discharging it for this application. An inspector or a coroner will treat it as the benchmark.

For detection, both electrochemical and infrared sensors will measure carbon dioxide. Infrared gives better accuracy and holds stability over time, where electrochemical sensors drift. The Ax60+ covers the fixed monitoring with infrared sensing, and the CO2 Buddy covers the portable check.

Carbon Dioxide Stunning In Abattoirs

Australian law requires animals to be stunned before slaughter, and carbon dioxide is one of the accepted methods for pigs.

The animal inhales carbon dioxide, blood oxygen falls, brain function is lost and death follows. To be certain the animal is irreversibly unconscious it has to remain at the point of maximum concentration for a defined period, generally three minutes. Inside the stunning system, concentrations run from zero to around 90 percent by volume, with the highest concentration at the bottom of the pit.

The gas detection requirement is not the process, it is the maintenance. Crews enter the pit to remove waste and to service and clean the equipment, and that entry is only permitted after the carbon dioxide has been extracted through ventilation and the CO2 system isolated. Before entry a sentry or team leader carries out atmospheric testing.

So there are two separate needs. Portable multi-gas detection with a carbon dioxide channel for the confined space entry, and fixed carbon dioxide detection for the maintenance crew while they are working, reporting through a controller and typically on to a site SCADA system.

Bulk carbon dioxide is held on site in large refrigerated vessels, which is a separate storage hazard in its own right.

Phosphine And Grain Fumigation

Phosphine is used to fumigate stored grain, and the exposure problem it creates is one most gas detection discussions get wrong.

Concentrations inside a fumigated silo can be well over 2,000 parts per million. Personal gas detectors for phosphine are ranged for exposure limits, typically around 3 parts per million full scale, because that is what protects a worker. Put a personal monitor into a fumigated atmosphere and it over-ranges immediately, which means it cannot tell you anything useful about whether the silo has cleared.

That mismatch is the practical issue. Personal monitors protect the person, and confirming a fumigated space has vented needs a different measurement approach.

Beyond the instrument, the control set for anyone inserting or testing phosphine is cotton overalls buttoned at neck and wrists, eye protection, elbow length PVC gloves, a respirator rated for gas and dust, and a personal phosphine monitor. Anyone else attending the site should also carry a phosphine monitor with a respirator available. Fixed or area monitors confirm an area is safe before it is entered.

The Grains Research and Development Corporation publishes a grain fumigation guide that sets out the practice in detail.

Dairy, Slurry And Silo Gas

Dairy production generates a gas mix that comes from decomposition rather than from process chemistry.

Methane forms through anaerobic digestion of organic material, and how much depends on how manure is stored and managed. Poor ventilation and higher temperatures increase it. Ammonia comes from the breakdown of nitrogen compounds in animal waste and slurry. Carbon dioxide accumulates in waste tanks and silos, and sealed silos and grain storage are particularly dangerous because carbon dioxide collects to the point where the space cannot support life without an external air supply. Hydrogen sulphide is heavier than air and sinks, which is why it concentrates low in poorly ventilated corners.

Nitrogen dioxide deserves separate mention because it is the one people do not expect. It is emitted from silos following chemical reactions in stored plant material, it has a bleach-like smell, and it produces a red brown haze. It can travel from a silo down chutes into areas where livestock are housed.

The places detection earns its keep are specific: when and where slurry is being mixed, during pumping and spreading, on and around the tractor during that work, in the stable during maintenance on slurry pumps and scrapers, near small openings and cracks in the floor such as around milking robots, low to the ground in poorly ventilated corners, and in slurry silos and tanks.

That is a mix of portable detection carried by whoever is doing the work and fixed detection where a hazard is permanent.

Who Regulates It

Food and beverage production falls under general work health and safety law rather than any industry specific regime, so the regulator is the state WHS regulator.

In Western Australia that is WorkSafe WA, in New South Wales SafeWork NSW, and in Queensland Workplace Health and Safety Queensland. Safe Work Australia writes the model laws and codes of practice but does not regulate or inspect.

Standards that apply depending on the application include AS 5034 for beverage dispensing gases, AS/NZS 5149 for refrigerating systems, and AS 2865:2009 for confined space entry, which covers cellars, silos, tanks and stunning pits.

What Gastech Supplies

Fixed gas detection for ammonia plant rooms, cellars, cool rooms, dispensing areas and stunning systems, with infrared sensing where carbon dioxide stability over time matters.

Open path detection for ammonia coverage across engine rooms and plant halls where a leak location cannot be predicted.

Portable single gas and multi-gas detectors for confined space entry, fumigation work, slurry handling and routine checks.

Area monitors for confirming a space is safe before entry, and controllers with the relay capacity to drive ventilation, shut off a gas supply and sound alarms inside and outside a storage area.

Behind them sit project engineering, NATA calibration and service, field service, fleet management and hire, from WA, NSW and QLD.

If you are working out whether a cellar meets AS 5034, or sizing detection for an ammonia plant room, talk to our Technical Consultants.