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Oxygen Deficiency Monitor and Cryogenics

An oxygen deficiency monitor and alarm is used to alert staff before they enter an area that may have critically low oxygen levels caused by a pressurized gas leak. This is especially useful in applications like cryogenics, cryotherapy, or cryofreezing that use liquid nitrogen, liquid helium, liquid oxygen, or any cryogenic gases.

A convenient way to transport gas is to pressurize it into a tank or cylinder. Gas tanks and cylinders are used in many different industries. Restaurants use tanks of carbon dioxide to carbonate sodas. Flower shops use cylinders of compressed helium to fill balloons. Even your outdoor grill uses propane gas to cook your burgers and hot dogs.

Across all these different uses for different gases, the one thing that they all have in common is that when stored under pressure, the gas becomes a liquid. If that tank is opened or leaks in an enclosed area, the gas will expand and lower the oxygen level. An oxygen sensor in an oxygen deficiency monitor is the only way to detect low oxygen levels.

The same is true in applications like cryogenics, cryotherapy, or cryofreezing.

Cryogenic Applications

Cryogenics is the production and behavior of materials at very low temperatures. Scientists use gases like hydrogen or helium that become a liquid at or below -292°F (-180°C) to freeze materials and study the changes caused by freezing. Cryogenics research has led to the creation of MRI machines, liquid oxygen rockets and superconductors.

Cryotherapy or cryosurgery uses liquid carbon dioxide, argon or nitrous oxide for external surgical procedures such as glaucoma, retinal detachment repair, removal of warts or skin cancers. It works by freezing the cells. In addition to external surgery, it can be used to kill tumors in the liver, kidneys, bones, lungs and breasts.

Cryo freezing or cryopreservation is most often used to rapidly freeze food by exposing it to liquid nitrogen or liquid carbon dioxide. The speed of the freezing minimizes the change of state while the food is being frozen. Because of the minimal tissue damage during cryofreezing, it has also been used on deceased humans who believe someday science will be able to revive them.

The College of American Pathologists has recently enforced new requirements that identify the potential dangers related to using and storing solid CO2 (dry ice) as well as liquid nitrogen and other gases used in cryogenics.

These specifications apply to clinics, reproductive facilities and laboratories to monitor safety in regards to oxygen deprivation after an incident of inhaling liquid nitrogen during a rescue attempt occurred in 2017.

Read more about cryogenics here.

Cryogenic Liquid Dangers

Cryogenic liquids have a normal boiling point below -130°F. At such low temperatures, argon, nitrogen, ethane, oxygen, methane and helium all become liquids. Thermopeida lists some of the most common cryogenic fluids.

All of the cryogenic gases are asphyxiates except for oxygen. An asphyxiate gas can be nontoxic or minimally toxic - but in every case it diminishes or displaces normal oxygen concentration in the air we breathe. Breathing in oxygen-depleted air can cause anything from shortness of breath to suffocation to death by asphyxiation.

While limited amounts of most cryogenic gases may not be harmful, a leak in a pressurized gas tank, fixture or line can become dangerous. For example, one volume of liquid nitrogen at its boiling temperature vaporizes to 696.5 volumes of nitrogen gas at room temperature. Therefore, even a small leak can quickly lower the oxygen level in a confined space. Monitoring the air using oxygen sensors for leak detection is a necessary safety requirement.

Cryogenic Liquid Safety

There are several precautions that must be observed when handling cryogenic liquids due to the extremely low temperatures. These liquids and their vapors can immediately freeze human tissue and cause many materials to become brittle or break under stress. Extremely cold cryogens, for example helium, have the ability to freeze the neighboring air.

A potential hazard is ruptures in the pressurized containers. A cryogenic liquid cannot be endlessly preserved as a liquid, no matter how well-insulated the container. The liquids in their sealed containers can produce excessive amounts of pressure that can cause the containers to rupture.

Another factor to keep in mind when dealing with vapors from cryogenic fluids are fog clouds. When extremely cold liquids are exposed to the atmosphere the gases thicken the moisture in the air and create a highly visible fog that can hover around cold equipment. Not only is oxygen deficiency a risk, but the cold can freeze human tissue and the cloud can make finding an exit difficult.

Ironically, one of the impacts of liquid nitrogen storage and handling can be oxygen enrichment. Because the boiling point of nitrogen is lower than oxygen, the nitrogen can “freeze” the oxygen molecules in place like snow crystals. As the oxygen returns to a gas, areas of high-oxygen levels can create a potential fire hazard.

Oxygen Deficiency Monitoring

oxygen deficiency monitor

For worker safety around cryogenic liquids, many facilities depend on personal oxygen deficiency monitors for the detection of low oxygen levels. These handheld safety alarms are useful during normal operations if the oxygen level gets too low, but do not solve the problem of entering an enclosed area with an ongoing gas leak. By the time a personal safety alarm sounds, the occupant could succumb to lack of oxygen.

An oxygen deficiency monitor is designed to solve this problem. Combining an oxygen sensor with a remote monitor, staff can be warned before they enter an area that has depleted oxygen levels. They can also monitor areas remotely. The oxygen deficiency monitor and alarm can be connected to the facility’s HVAC system, or can notify emergency first responders of a gas leak.

References:

https://www.airproducts.com/~/media/Files/PDF/company/safetygram-16.pdf

https://ehs.research.uiowa.edu/liquid-nitrogen-handling

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


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