This document provides recommendations and guidance for safely managing the use of nitrogen gas. The intent is to focus personnel actions so they are aligned with the clear understanding that even limited inhalation of concentrated nitrogen gas can be lethal.
This document addresses training and communication, nitrogen use, and the management and identification of nitrogen distribution facilities. Other applications of and uses for nitrogen gas not specifically mentioned should be managed in keeping with this procedure.
Provisions contained in this guidance for safely managing nitrogen gas may be used to manage other asphyxiant gases (e.g., argon, carbon dioxide, and helium).
Management and Supervisor have the responsibility to implement this guidance for safely handling nitrogen gas.
Nitrogen gas hazard summary
Inhaling air that has a high concentration (i.e., >90 percent) of nitrogen gas can cause rapid suffocation. Only one or two breaths of pure nitrogen can cause death.
Nitrogen is a nontoxic, colorless, odorless, tasteless gas that is slightly lighter than air (vapor density of 0.97). Nitrogen comprises 78 percent by volume of the air we breathe. Nitrogen is a simple asphyxiant that causes injury by displacing oxygen in air. Concentrations of about 80 percent or higher can negatively affect people’s ability to perform work safely. Inhaling nitrogen-enriched air may cause dizziness, drowsiness, nausea, vomiting, excess salivation, diminished mental alertness, loss of consciousness, and death.
A person’s life may be endangered before the signs or symptoms of overexposure to nitrogen become apparent. Personnel overexposed to nitrogen should be immediately moved to fresh air; prompt medical care should be sought. Consult MSDS Central for additional information on the hazards and symptoms of nitrogen gas exposure.
Nitrogen gas is used widely throughout the oil & gas, petroleum, chemical industries, and it is important that it be properly managed to prevent personnel overexposure to this asphyxiating substance.
Note: Liquid nitrogen is a source of nitrogen gas generation.
Nitrogen gas use
Nitrogen gas should not be used for the following purposes:
- For general surface cleaning, including process areas, maintenance shops, outside work areas, and the outside surface of any equipment (This prohibition does not apply to process use of nitrogen gas as a purging medium where the discharge is to a controlled location [e.g., a high vent location where there is no potential for personnel exposure].)
- For driving pneumatic tools
- As a substitute or back-up for process or instrument air, unless a documented risk assessment that identifies all potential hazards and risk reduction measures has been completed and a documented administrative system is in place to safeguard against unintentional personnel exposure to nitrogen gas
- As an agent in an engineered emergency, total-flooding, fire-suppression system to extinguish fires or cool reactive materials in an area that is or could be occupied by personnel
Where nitrogen gas is used and vents, or could vent, to an area occupied or potentially occupied by personnel, a documented risk assessment should be performed. This assessment should address such concerns as planned and unplanned venting, including nitrogen gas venting from open manways; collection of nitrogen in such areas as confined spaces, control rooms, and analyzer rooms; and personnel exposure potential. If potentially hazardous oxygen concentrations (i.e., 19.5 percent or less) are possible, warning signs and control measures must be in place to prevent personnel exposure. These control measures could include oxygen meter monitoring; audible alarms; forced air ventilation; barricades; capping, plugging, blanking, or locking nitrogen lines; or other control and warning devices.
Contractors who perform work at the facility should not connect to or use nitrogen gas, unless a written managing process (e.g., a formalized permit system or standard operating procedure) for contractor use is in place. Contractor fittings should conform to facility standards.
Nitrogen gas facilities
To manage safely all nitrogen lines and facilities, the site/unit should have:
- All nitrogen lines a unique standard color of blue for identification purposes;
- Nitrogen gas systems should be identified so that they are clearly visible and can be easily traced to the source;
- All means of identifying should be uniform across the site; and
- Hoses used for nitrogen service will be blue (typical in the industry). These should be the only blue hoses used on the site/unit.
Nitrogen lines should not be interconnected to breathing-air lines under any circumstances.
Nitrogen gas access stations
The number of nitrogen gas access stations should be minimized. A review of nitrogen gas stations should be performed at least once every three years to determine if the number of these access stations can be further reduced. An inventory of nitrogen gas access stations and/or locations should be maintained and updated every three years to document the review.
Makeshift or temporary nitrogen access stations should not be allowed except under stringent administrative controls. All makeshift or temporary nitrogen access stations should comply with all mandatory requirements in this guidance. All makeshift or temporary nitrogen access stations should be removed immediately after the need has passed.
Screwed pipe, unions, and flanges are preferred for nitrogen service connections. Quick-connect/disconnect couplings for nitrogen gas stations should not be used unless special controls are followed. At a minimum, these controls must include:
- A managing process to control the use of all quick-connect/disconnect couplings.
- A requirement that nitrogen gas couplings should be unique and uniform across the site/unit.
Required connection points will be permanently installed (hard piped tubing connections, hoses banded in place, hard piped to fixed facilities, pipe flange for blow out, etc.)
Nitrogen outlets, when not in use, should be plugged or capped.
Signs, labels, and color coding
Nitrogen gas systems should be identified so that they are clearly visible and can be easily traced to the source. All means of identification should be uniform across the site. Appropriate warning signs, along with labels or color coding, should be used at the point of connection.
Each Nitrogen station will have a warning sign posted at the station or on the valves. The warning sign will picture the skull and cross bones and state "Danger Nitrogen Fatal if used for breathing air. Do not use in a vessel or confined space.
Following is an example of the warning sign to be used. 8 x 8 diamond shaped sign with a blue skull and crossbones. Below the skull and crossbones, the OSHA DANGER sign and the following wording:
Fatal if used for breathing air