Use of Liquid Oxygen

August, 2004

Information Bulletin 04-15

Use Of Liquid Oxygen

Attachment 1: Locations Used For Transfilling of Liquid Oxygen


The use of liquid oxygen in health care facilities has increased dramatically in the past few years. This Information Bulletin outlines the basic requirements of National Fire Protection Association Standard 99 (NFPA 99) for the safe storage, transfer and use of liquid oxygen in a health care facility. The 1999 edition of NFPA 99 is adopted by reference in the 2000 edition of NFPA Standard 101 ( Life Safety Code ).


Transferring (also referred to as transfilling) of liquid oxygen from one container to another presents several potential hazards, which include the:

  • Strong oxidizing properties of oxygen,
  • Very cold temperature of the liquid and vapor (it's classified as a cryogenic fluid), and
  • Pressure producing potential of the vaporization and/or liquid expansion processes.

Here are some important elements to remember relating to the storage and use of liquid oxygen:

  • The transfer of liquid oxygen from one container to another can create an oxygen-enriched atmosphere within the vicinity of the containers. When a liquid oxygen container is not used for a period of time, there is a small amount of oxygen vented into the vicinity of the container. If the container is tipped over or placed on its side, a larger amount of oxygen will be vented. This venting may create an oxygen-enriched atmosphere if the container is stored in a confined space.

  • In an oxygen-enriched atmosphere, materials that are combustible and flammable in air ignite more easily, burn more vigorously and produce a higher temperature when burning. Materials not normally considered to be combustible may be so in an oxygen-enriched atmosphere. Examples of these types of materials that may be found on or near patients/residents in health care facilities can include hair oils, oil-based lubricants, skin lotions, facial tissues, clothing, bed linens, alcohols, acetone and some plastics. Absorbent materials such as clothing or bedding, for example, may become saturated with oxygen when exposed to oxygen or an oxygen-enriched atmosphere and more readily ignite in the presence of a source of ignition.

  • A hazard can also exist if the oxygen equipment becomes contaminated with oil or grease. It is important to keep liquid oxygen separated from sources of ignition.

  • Unfortunately, there are many items in a typical patient/resident room in health care occupancies that can create a source of ignition if introduced into an oxygen-enriched atmosphere. These can include electric wheelchairs, electric razors, electric bed controls, hair dryers, remote television controls, television sets, radio and stereo equipment, computers, air conditioners, telephone handsets and fans.

Here are two other points to be aware of relating to the temperature and vaporization hazards:

  • Liquid oxygen boils at –297.3 degrees Fahrenheit and is extremely cold. If permitted to contact skin or non-protective clothing, cold surfaces present on liquid oxygen systems such as valves, lines or couplings can cause severe frostbite or cryogenic burns. Skin will stick to cold surfaces at cryogenic temperatures, causing additional injury.

  • One volume of liquid oxygen at standard atmospheric pressure when warmed will expand significantly and when vaporized will produce approximately 860 volumes of gaseous oxygen at ambient temperatures. The large volume of gaseous oxygen resulting from the vaporization of liquid oxygen has the potential, if trapped in a closed circuit not adequately protected by pressure relief devices, to generate gas pressures high enough to cause explosive rupture of containers, transfer lines, piping, and other system components.

Frequently Asked Questions:

What is considered storage and what is considered use?

A single base container, or multiple manifolded containers, of liquid oxygen that is assigned to a specific resident, is providing oxygen to the resident through a physical connection, or is ready to provide oxygen to the resident through a physical connection is considered in use in that resident's bedroom. It is acceptable to have one base container or a manifold of containers and one small (2-liter) portable container assigned to the same resident concurrently in the bedroom. It is also acceptable to have a base container or manifold of containers assigned to each resident in a multi-bed room. Each of these residents may also have a portable container in their bedroom. If using a manifold of containers, the facility must be able to provide a physician's order supporting the need for multiple containers to meet the prescribed administration rate.

Additional base containers or small portable containers assigned to a resident and kept in that same resident's bedroom are considered to be in storage . Base containers or small portable containers that are not connected to a resident and are placed in the means of egress, common spaces, nurse station or other rooms within the facility are considered to be in storage .

How many cubic feet are in a liter of liquid oxygen?

Base containers for liquid oxygen are available in several capacities. Base containers are commonly 31 or 41 liters in capacity.

A liter of liquid oxygen at 70 degrees Fahrenheit and 14.7 pounds per square inch (psia) is equal to 30.4 cubic feet of gaseous oxygen. Using this conversion factor, multiply the number of liters in the base container of liquid oxygen by 30.4. The resulting product is the number of equivalent cubic feet of oxygen. For example, 41 liters of liquid oxygen times 30.4 equals 1246.4 cubic feet of oxygen. A 41-liter base container is equivalent to 1246.4 cubic feet of oxygen at standard pressure and temperature.


The storage of nonflammable gases is addressed in NFPA 99, Sec. 8-3.1.11. Storage requirements are divided into two categories - requirements for quantities less than 3000 cubic feet and requirements for quantities more than 3000 cubic feet. Using the conversion factors outlined earlier, it follows that three (3) 41-liter containers of liquid oxygen in storage exceeds the threshold 3000 cubic feet. Here are some important points to remember about the storage of liquid oxygen:

Storage of liquid oxygen that is less than the equivalent of 3000 cubic feet:

The requirements for storage of nonflammable gases in quantities less than 3000 cubic feet can be found in NFPA 99, Sec. 8- Indoor storage is required to be in a locked enclosure and properly separated from combustible or incompatible materials. Sources of ignition are prohibited within the storage location and oxygen cannot be stored with any flammable gas, liquid or vapor. Sec. 8- also makes references to a number of other sections of NFPA 99.

Storage of liquid oxygen that is more than the equivalent of 3000 cubic feet:

The requirements for storage of nonflammable gases in quantities greater than 3000 cubic feet can be found in NFPA 99, Sec. 8-, which requires compliance with Sections 4- and 4- of NFPA 99. In addition to the requirements outlined in the previous paragraph, such storage locations must be enclosed with construction providing a fire-resistance rating of at least one hour. Such locations shall also be vented to the outside by a dedicated mechanical ventilation system (natural ventilation is allowed where the storage location has at least one exterior wall).

Transferring Liquid Oxygen From One Container To Another:

NFPA 99, Sec. 8- addresses the transferring liquid oxygen from one container to another. This section specifically addresses where transferring can occur within a facility, but references two Compressed Gas Association (CGA) Pamphlets for the types of equipment allowed to be utilized for transferring and for the use and operation of small portable liquid oxygen systems. Although the CGA pamphlets also address where transferring can occur, the Centers for Medicare and Medicaid Services (CMS) has determined that the location requirements of NFPA 99, 8- take precedent.

Sec. 8- makes no distinction in the size (capacity) of either the donating or receiving container. Therefore, these requirements are applicable whether transferring liquid oxygen from one base container to another or from a base container to a 2-liter portable container.

Sec. 8- requires that the transferring of liquid oxygen from one container to another inside the facility be accomplished in a room specifically designated for the transferring. Refer to attachment #1 at the end of this Information Bulletin for specific requirements for this room.

Sec. 8- specifies that:

  • Transferring shall be accomplished utilizing equipment designed to comply with the performance requirements and procedures of CGA Pamphlet P-2.6, Transfilling of Low-Pressure Liquid Oxygen to be Used for Respiration , and adhering to those procedures.

  • The use and operation of small portable liquid oxygen systems shall comply with the requirements of CGA Pamphlet P-2.7, Guide for the Safe Storage, Handling and Use of Portable Liquid Oxygen Systems in Health Care Facilities.

The 2000 edition of CGA Pamphlet P-2.7 refers to transferring of liquid oxygen as “transfilling”. This Pamphlet provides further guidance regarding transferring. Sec. 5.2.1 states that: “An oxygen-enriched atmosphere constitutes a potential fire hazard. Filling of base unit oxygen containers should be performed only in an area outside the facility that is as large and open as possible. An active ventilation system will also help to lessen oxygen buildup. Filling performed inside a building should be limited to the portable unit only. Areas used to exit the building should not be used for filling or storage of liquid oxygen systems.”

Sec. 5.3 of that pamphlet states: “Because the atmosphere may become oxygen enriched by venting of the containers during filling, use, or storage, it is important to remove sources of ignition from the immediate area. Filling and use should occur a minimum of 5 feet away from electrical appliances. Cigarettes, cigars, pipes, matches, cigarette lighters, candles, fireplaces, and other sources of open flame must not be used in the same room where liquid oxygen systems are filled, stored, or used.”


It is very important that transferring of liquid oxygen be performed only by properly trained and qualified persons who are familiar with the precautions necessary to avoid the hazards listed previously. It is equally important that the oxygen vendor provide written operating instructions for the safe transfer of liquid oxygen and that those instructions be carefully followed.

The new Life Safety Code survey documents specifically address the requirements for transferring liquid oxygen from one container to another at tag K-143. The safe use and storage of liquid oxygen are addressed at tag K-076. Deficiencies will be issued if the requirements of NFPA 99 are not met.

The Department strongly recommends that a facility that is considering the use of liquid oxygen review and become familiar with all of the applicable requirements of NFPA 99 (1999 edition). Although attachment #1 details the major requirements for a liquid oxygen transfer room, facilities are encouraged to obtain a copy of the standard in order to become familiar with all the requirements that are applicable to certified health care facilities. Further, the facility should identify a room or rooms that comply with the aforementioned requirements for transferring liquid oxygen.

Copies of NFPA 99 (1999 edition) are available from the National Fire Protection Association in Massachusetts. The NFPA can be reached at 1-800-344-3555.

Copies of the CGA pamphlets are available from the Compressed Gas Association in Virginia. The CGA can be reached at 703-788-2700. It is our understanding that you must be a member of CGA to purchase these pamphlets.

This information bulletin was authored by the Minnesota Department of Health, Health Regulation Division, and the Minnesota Department of Public Safety, State Fire Marshal Division. If you have any questions about this information bulletin, please contact either Engineering Program Manager, at 651-201-3710 or Mr. Robert L. Imholte, Deputy State Fire Marshal Supervisor, at 320-685-8559.  Mr. Imholte's email address is

Attachment #1: Locations Used For Transfilling of Liquid Oxygen

This attachment outlines the major requirements that apply to rooms used for the transfer of liquid oxygen from one container to another. The contents herein are based on provisions found in Chapters 4 and 8 of the 1999 edition of NFPA 99 and Chapters 27, 30 and 32 of the 2003 Minnesota State Fire Code.

  1. Such rooms must be completely enclosed with a fire barrier of minimum 1-hour fire resistive construction. This includes:
    1. Each component of the room (i.e., the floor, all four walls and the ceiling) must have a fire-resistance rating of at least 1 hour.
    2. The door into the room must be a listed assembly having a minimum fire resistance rating of 45 minutes. Listed assemblies include the door, frame, and self-closing and positive latching hardware.
  2. Flooring must be ceramic or concrete. A concrete floor must be bare. It is not acceptable to paint the concrete floor.

  3. The room must be provided with complete automatic sprinkler protection. Depending on the size of the room, one sprinkler head may suffice.

  4. The room must be mechanically ventilated as follows:
    1. The exhaust fan must provide a minimum of one cubic foot per minute (CFM) of exhaust for each square foot of floor area within the room. For example, a room measuring 36 square feet in area must have a minimum of 36 CFM of exhaust ventilation.

    2. Room exhaust and make-up air must be arranged so as to prevent the accumulation of oxygen gas anywhere in the room. To best accomplish this, the exhaust should be located at, or within 6 inches of, the ceiling. Make-up air should be at, or within 6 inches of, the floor.

    3. The exhaust system must be dedicated to that room only. It is not acceptable to connect the exhaust fan to any other duct system.

    4. The exhaust must go directly to the outside. If the exhaust must go through other areas either adjacent to or above the transfer room, the ductwork must be installed inside of an enclosure with a fire-resistance rating of at least 1 hour.

    5. The exhaust fan must operate at all times the transfer of oxygen is taking place. This can best be assured by inter-locking the fan with the room lighting. If the room is also used for the storage of oxygen, the exhaust fan must be arranged to operate continuously.
  5. Electrical equipment and wiring in oxygen storage and transfer rooms are not required to be explosion-proof. On the other hand, however, electric wall fixtures, switches and receptacles are required to be at least 5 feet above the floor as a precaution against their physical damage.

  6. If the room is also used for oxygen storage, it must be kept locked against unauthorized entry.

  7. Approved signage must be posted on the room door. The exact language of the required signs is at the discretion of the facility, but the signs must clearly indicate that transfilling of liquid oxygen is occurring and that smoking in the immediate area is prohibited. Immediate area involves more than the room.

Updated Friday, February 06, 2015 at 03:40PM