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Combined Oxygen Depletion

Oxygen Depletion & Carbon Dioxide Application Example

Combined Oxygen Depletion and Carbon Dioxide Enrichment Monitor in a Laboratory Environment

The Risk

If Liquid Nitrogen or Carbon Dioxide is allowed to escape into the air, the Oxygen level is depleted. Since Liquid Nitrogen expands rapidly after it is released (1 litre of LN2 can expand to 680 litres), even a small amount of Liquid Nitrogen can, if released, reduce the Oxygen concentration by enough to cause danger. Carbon Dioxide even at low levels can be harmful to health, and notice should be taken of ensuring compliance with the EH40 Workplace Exposure Limits document. Depleted Oxygen levels are not just deadly, but impair physical and mental ability leading to an increased risk of accidents and other physical problems – see the section covering Oxygen, Carbon Dioxide and Liquid Nitrogen in our Gas Information page for more details.

In the laboratory environment, it is often found that Liquid Nitrogen Dewars are of sufficient volume that if released, they would completely dispel the Oxygen from the room. Whilst extraction is normally provided, it is often switched off during non-operating hours, but the nitrogen may still leak – this provides a common high risk of an Oxygen depleted environment. Additional risks exist from poorly designed or failed ventilation and other gas discharge. Whatever the specific risks, you can safeguard personnel against the danger of asphyxiation due to depleted oxygen by installing an Oxygen Depletion Alarm.

The Solution

Utilising the basic functions of our Gas Alarm System, users of Carbon Dioxide or other gases can monitor up-to 36 points around the workplace using our SafeGuardTM system, or alternatively up to 8 using the extremely cost effective SafeGuardLiteTM.

The Oxygen and CO2 sensors are distributed in the areas at risk, and are monitored by the central monitoring station. In a normal working environment, sensors are normally situated at around 1.25 metres above floor level for Oxygen, and 300mm for CO2 – but this of course would be tailored to suit the circumstances of the application. We can advise you on the best location for the sensors during a site survey. The Oxygen sensors usually have a range of 0-25% and are of the electro-chemical type. The Carbon Dioxide sensors are usually 0-2% and are of the Infra-Red dispersion type. The system is normally set to give a first stage warning alarm at 19% Oxygen or 0.5 CO2, and then a second stage full alarm at 17.0% Oxygen or 1.5% CO2. This enables action to be taken before an evacuation is required, and evacuation before danger.

The system has a User Interface, which is a an LCD (optional touch screen) control panel. Here it is possible to view the readings from the gas sensors, and indication is made audibly and visually if the system detects an alarm condition. Normally sited with the User Interface is a small printer, which can be utilised to take records of testing, alarms and system set-up. It is advisable that the User Interface is located outside of the risk area, so that in the event of an alarm, the information from the system can be accessed without entry into the risk area.

In this example, the system could be used to switch on or increase the speed of ventilation to the risk area to ensure acceptable Oxygen and Carbon Dioxide levels. The system has two alarm settings. The first (Amber) Alarm can be utilised to trigger the ventilation, and the second (Red) Alarm be utilised to indicate evacuation of the area. The audible alarm is only triggered at the second (Red) Alarm stage. Either Alarm stage could be utilised to shut off the bulk storage supply of gas.

Application Specific Options

  • It is possible for the system to monitor multiple rooms, floors or even buildings, with area specific (zoned) alarm outputs.
  • Attractive sensor enclosure for Laboratory / Office environments
  • Separate Interface Panel and monitoring station – ideal in the Lab environment where wall space is limited, or where the Interface needs to be in a corridor or central area. This can also reduce installation cost where the Interface Panel is located at a distance from the sensors.

If you would like more information about Oxygen Depletion & Carbon Dioxide Alarms or to book a no obligation consultation/survey, please contact us.