Oxygen Depletion Deficiency Alarm Monitor

An oxygen depletion alarm or oxygen deficiency monitor constantly monitors oxygen levels in a room and warns occupants of low oxygen levels.

• Oxygen depletion alarms are wall mounted near stored gases like nitrogen, helium and argon.
• If one of the stored gases is released or inadvertently leaks into the air, the oxygen sensor detects the low oxygen level and displays it on the monitor.
• If the oxygen level is too low it automatically activates an alarm to warn the occupants of oxygen deficiency in the room.
• In some applications an oxygen deficiency monitor can also act as a room air controller, switching on fans bring in fresh air.

Room oxygen depletion alarms or oxygen deficiency monitors are critical in any room or enclosed area in which low oxygen levels can occur.

Normal Oxygen Levels in Air

By volume, dry air contains 78.09% nitrogen, 20.95% oxygen 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.

At normal temperatures and pressures, 20.9% oxygen in the air is considered optimal for humans. When oxygen levels drop below 19.5% hypoxia (lowered oxygen levels) begins to occur. The air is considered oxygen-deficient, although it is still relatively safe for short periods of time or for people who have acclimated their bodies to lower oxygen levels.

Why are Oxygen Deficiency Monitors Important? 

Oxygen deficiency at levels below 16% is dangerous for human life. The challenge is that the difference between 16% and 21% is typically made up of inert, odorless gases like nitrogen, argon or carbon dioxide, so the oxygen deficiency may not be noticed immediately. If oxygen levels remain low, sudden unconsciousness or death without symptoms may occur.

Where are Oxygen Deficiency Monitors Used?

Oxygen depletion alarms are used in any place where low oxygen levels can occur. While most people think of a closed environment like an airplane or submarine, a much more common example is a room where pressurized cylinders of hydrogen, helium, argon, or nitrogen are stored. If a hose or fitting leaks, the depressurization of the gas storage system can rapidly lower the oxygen level in the room.

Examples of stored gases where oxygen depletion alarms are necessary include:

• Nitrous oxide or nitrogen used in hospitals
• Liquid helium to cool MRI machines
• Liquid nitrogen, helium or argon for cryo-biology, IVF, cryosurgery or other types of cryogenic research
• Liquid nitrogen to package meats, fruits, or dairy
• Argon or other shield gases for welding
• Nitrogen and argon used in 3D printing
• Argon or other inert gases for fire suppression

While carbon dioxide could be added to this list, common practice is to use a CO2 Safety Alarm to measure high CO2 levels instead of an oxygen deficiency alarm.

OSHA Requirements for Oxygen Depletion Alarms

OSHA's 29 CFR 1910.146, "Permit Required Confined Spaces," contains the requirements for practices and procedures to protect employees in general industry from the hazards of entry into permit-required confined spaces.

The standard defines an oxygen-deficient atmosphere as any atmosphere containing less than 19.5 percent oxygen by volume. Any atmosphere that contains less than 19.5 percent oxygen is hazardous and may not be entered by unprotected workers.

The device alarm and warning levels should be where the oxygen concentration is below 19.5% or above 23.5% oxygen concentration levels.

NIH Oxygen Monitoring Devices Protocols

While not law or an OSHA regulation, the National Institutes of Health Protocol for use and maintenance of Oxygen Monitoring Devices has been established to provide guidance on the installation, maintenance, and calibration of oxygen monitoring devices in animal and laboratory areas in all NIH owned and leased buildings. It states:

"An oxygen monitoring device shall be installed in any indoor location where compressed gases or cryogenic liquids are stored and/or dispensed in manner that could create the potential for the displacement of oxygen. At a minimum, the following factors should be used in determining if a device should be installed: manufacturer (e.g., magnet) guidance, volume of gas used, location of gas, and air changes/hour in the room/area. The 2008 NIH DRM notes that both ‘carbon dioxide manifold rooms… [and] nitrogen holding rooms and shall include oxygen level monitoring alarms’ (section 8, pages 8-80). Additionally, compressed gases or cryogenic liquids shall not be located or dispensed in any indoor location that does not have proper ventilation.

Where Should Oxygen Depletion Alarms be Located?

All gases have molecular weight. Depending on the gas weight, as it displaces air with oxygen, over time it will tend to collect or pool higher or lower in a room.

The molecular weight of air is 29. Therefore, in areas that are unoccupied, when testing for gases that are heavier, the oxygen sensor should be mounted lower on the wall in a room. When testing for gases that are lighter, the oxygen sensor should be mounted higher. 

Here is a list of where to mount the oxygen sensor on a wall for the most common gases:

1. Mount 18 inches from the floor when testing for refrigerants, chlorine, butane, propane, CO2, nitrous oxide, argon
2. Mount 48 inches from the floor when testing for ethylene, carbon monoxide, ammonia, nitrogen
3. Mount 60+ inches from the floor when monitoring hydrogen or helium

This chart lists the most common stored gases by molecular weight, with the lightest gases on top and the heaviest gases on the bottom.

Note that in rooms that are continuously occupied, it makes sense to put the oxygen depletion sensor close to the pipe or fittings where a gas leak is most likely to occur.

Selecting an Oxygen Deficiency Monitor

When looking for an oxygen deficiency monitor, there are some features to consider:

• Does it meet OSHA and NIH specifications? Oxygen detectors should alarm at 19.5%, and 17.5% to comply with Occupational Safety and Health Administration and National Institute of Health guidelines.
• Is it hard-wired? While wireless oxygen detectors are easy to install, the sensor should be hard-wired to the remote display to guarantee that a WiFi or network failure does not disable the alarm.
• Is it easy to install? Using an electrician to install the monitor will add significantly to the price.
• Does it come with support? Oxygen detection is easy, but knowing when or how to use it can be challenging. Can you speak with an engineer for experienced before and after sale support?
• Is it dependable? In most cases an oxygen deficiency monitor is an install once and forget it device. If the sensor fails it should inform you on the display.
• Can it control the HVAC system? If you want the alarm to open a vent or turn on a fan to clear the air, does it have relays or industry standard outputs you can use?
• Is it upgradeable? In noisy factory environments can strobes be added? Can you attach one or more remote displays to warn occupants of oxygen deficient air before they enter a room?

Oxygen Deficiency Alarm with Remote Sensor 

To warn occupants of oxygen depletion in an enclosed area or room, oxygen deficiency monitors are used. These include two components:

• An oxygen sensor housed in a case with audible and visual alarms to warn occupants in the confined space
• One or more remote monitors with duplicate audible and visual alarms to warn personnel outside the space and before entering the room

The two components are linked by a cable that sends the oxygen level data and power from the monitor to the remote display in real time. Typically a wireless connection is avoided as problems with networks and interference from building materials like concrete and steel render the system useless.

In addition to the sensor and remote display(s), a data link can be made utilizing the devices 4-20 ma output between the sensor and a control panel or dashboard to warn offsite personnel if an oxygen depletion alarm has occurred.

Oxygen Depletion Safety Alarm

Our Oxygen Depletion Safety Alarm is designed to protect customers and workers near stored inert gases like nitrogen, argon, helium, nitrous oxide, welding gases and more.

This oxygen monitor has both audible and visual alarms. 3 built-in relays are triggered at 19%, 17%, and 15% respectively that can control an exhaust fan or send an alarm to the fire department or monitoring company. The alarm levels are user configurable to allow for specific applications.

Personal Oxygen Safety Monitor

For industries that require an alternative adjunct to the Remote Oxygen Depletion Safety Alarms, CO2Meter offers the SAN-20 Personal Oxygen Safety Monitor.

The SAN-20 is designed specifically for employees who work in enclosed areas where oxygen depletion may cause personal harm or asphyxiation. 

The Personal Oxygen Safety Monitor, features a man down alarm that is triggered when an employee fall occurs, audible/visual alarms and a vigorous vibration. 

The need for monitoring oxygen levels in a room can be critical for those working and handling the gas type, and CO2Meter strives in being able to provide fixed and personal devices, that continue to save lives today. 

References:

https://en.wikipedia.org/wiki/Atmosphere_of_Earth

https://www.ccohs.ca/oshanswers/safety_haz/welding/fumes.html

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.146