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CO2/ O2 Monitoring for OH&S Compliance as per AS 5034

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Alvi Technologies  specialises in non-hazardous and hazardous gas detection products as well as services. This article discusses carbon dioxide toxicity and oxygen depletion hazards as well as OH&S compliance requirements as per AS 5034 with specific reference to beverage dispensing environments.  


Accidents have occurred in the dispensing of beverages due to lack of understanding of the potential damage high pressure inert gases can cause.  

High pressure cylinders in the supply systems for beverage dispensing can supply pressures up to 24000 kPa. Due to all gas systems being under pressure, it is possible that the system and equipment connection may develop a leak causing a build-up of inert gases in cellars and low level areas that could potentially lead to asphyxiation of personnel working in these areas.  

As per AS 5034, all installations using inert gases for beverage dispensing should be assessed for risk and control measures should be implemented.  

Carbon Dioxide Toxicity and Oxygen Depletion Hazards  

Toxicity Hazard of CO2:

Carbon dioxide is toxic as it creates an oxygen deficient atmosphere. CO2 concentration of 3% - 5% in the air can cause respiration problems and headaches. Higher concentrations can cause rapid circulatory deficiency leading to coma and death.  

Oxygen Depletion:

Normal oxygen in the air is around 21% and the balance is from inert gases such as Nitrogen, CO2, Argon and Krypton. Oxygen concentration of less than 21% Vol is a threat to life through asphyxiation.  

Compliance to OH&S as per AS 5034 

  • Mandatory CO2 and Oxygen alarm systems (if N2 or Argon used), generating adequate warning/alarm if limits exceed
  • Mandatory safe system of entry and work including use of appropriate personal protective equipment and self contained breathing apparatus, wherever required
  • Manual activation of mechanical ventilation systems or automatic activation from gas monitoring systems and gas alarm systems (recommendation only)
  • Monitoring of CO2 and generating adequate warning/alarm at TWA (0.5% Vol) and STEL (3% Vol) levels
  • Maintenance of Oxygen levels above 19% Vol (where inert gases such as N2 and Argon are used) and the generation of an alarm if level falls < 19% Vol
  • Installation of CO2 sensors at 0.3 – 0.6m above floor levels (slope of floor, partitions and air flow must be considered)
  • Visible and audible alarms to be provided both inside the risk area as well as outside (near the entry door)
  • Fixed systems must be hard-wired to prevent unauthorised persons from switching off the system (battery backup may be considered)
  • Regular servicing and maintenance of the systems must be undertaken, including six-monthly testing and calibration of the gas monitoring systems with records of maintenance (as per manufacturer’s guidelines)

Sizing and Selection of CO2 (O2) Cellar Alarm for Dispensing Systems

There are a number of systems available on the market for monitoring of CO2 and O2 in pubs, cellars, cool rooms, cylinder storage rooms and transportation vehicles. Before making a decision, one must fully understand one’s requirements. 

  • Number of cool rooms as well as cylinder storage rooms and their dimensions
  • Number of entry doors
  • Is only CO2 monitoring required?
  • Does the system need to automatically switch on the ventilation fan?
  • Cost of ownership in getting the sensors serviced and calibrated every 6 months
  • Is an integrated unit required where the sensors and gas controller are all built into one unit and installed inside the risk room?
  • Alternatively, should one choose a gas controller with remote sensors where the gas controller is installed outside the risk room and only the O2 or CO2 sensors are installed inside the risk rooms?
  • Are the sensors protected against short circuit or reverse polarity?
  • Does the system work on 24 V DC (less of an electrical hazard) with the option of 240 VAC operation?
  • Does the gas controller have a test function that can test all the relays, alarms, alarm LEDs and alarm buzzers?

Specifications of a Cellar Alarm System

A typical CO2 system shall consist of one gas controller installed outside the risk room near the entry door and connected up to one or two remote CO2 or O2 sensors.  

Larger premises require a multi-channel system that is modular and expandable from 4 to 16 remote sensors for CO2 and O2, and even refrigerants such as R134a and R410a. The system will continuously monitor the area for any excessive build-up of CO2 or an oxygen-deficient atmosphere and generate adequate warning via the connected audio visual alarms.  

Additionally, the system will have outputs for connecting to the Building Management System, PLC and SCADA or triggering the ventilation fan.  

Please refer to AS 5034 for additional guidelines including detailed specifications, signage, training as well as personal and respiratory protection programmes required for the installation of cellar alarm systems. 


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