NIOSH warns HCWs about anesthetic gases

Make sure 'scavenging' systems are working

Operating room and recovery room personnel may be exposed to waste anesthetic gases without realizing the danger, and employers should take steps to make sure their ventilation and gas "scavenging" systems are working properly, according to a new informational brochure from the National Institute of Occupational Safety and Health (NIOSH).

Health care workers can suffer from symptoms that include headache, fatigue and nausea from exposure to high concentrations, as well as possible long-term effects such as liver or kidney disease and reproductive problems, NIOSH said. Yet health care workers cannot detect the gases until they are many times higher than the recommended exposure limits, the agency said.

Workers may be exposed when they hook up or disconnect the scavenging and venting system or if there are leaks in the system, NIOSH said. The gases also may be exhaled by recovering patients or may seep from loose-fitting patient masks.

The information brochure on anesthetic gases is one of a series being published by NIOSH while the agency revises a larger health hazards book for health care. NIOSH also is seeking to take a closer look at waste anesthetic gases and has asked for information on the new anesthetic agents isoflurane, desflurane, and sevoflurane in a Federal Register notice, says Charles L. Geraci, PhD, CIH, chief of the document development branch in NIOSH's education and information division in Cincinnati.

"There are some new generation anesthetic agents on the market. They do require a higher volume to be delivered due to lower potency," says Geraci. "What we really need to do now is get a better handle on the new agents."

The Occupational Safety and Health Admini-stration has voluntary guidelines but no regulatory exposure limit for anesthetic gases. (See NIOSH has not revised its recommended exposure limits since 1977, when it set a limit of 25 parts per million (ppm) for nitrous oxide if it was the sole agent used, measured as a time-weighted average during anesthetic administration. NIOSH also recommends a ceiling limit of 2 ppm for certain halogenated anesthetic gases (chloroform, trichloroethylene, halothane, methoxyflurane, fluroxene, and enflurane) in a sampling period of no more than an hour.

The American Conference of Governmental Industrial Hygienists set a threshold limit of 50 ppm as a time-weighted average over an eight-hour workday for nitrous oxide and halothane and 75 ppm for enflurane. There are no recommended limits for the commonly used anesthetics isoflurane, desflurane, or sevoflurane.

NIOSH recommends that employers take the following measures to reduce exposures:

  • Establish a hazard communication program.
  • Develop and implement a safety and health plan that includes information about exposure hazards and methods to control them.
  • Label cylinders containing anesthetic agents.
  • Make material safety data sheets (MSDS) available.
  • Train workers as required by the Occupational Safety and Health Administration (OSHA) hazard communication standard [29 CFR 1910.1200].
  • Install a scavenging system with the anesthesia delivery system to remove waste anesthetic gases from the operating room. Place the exhaust in an area where waste gases will not be reintroduced into intake air for the facility.
  • Install a ventilation system that circulates and replenishes the air in operating rooms (at least 15 air changes per hour, with a minimum of three air changes of fresh air per hour).
  • Install a ventilation system that circulates and replenishes the air in recovery rooms (at least six air changes per hour, with a minimum of two air changes of fresh air per hour) to prevent exposure to waste anesthetic gases exhaled by patients.
  • Properly maintain anesthesia machines, breathing circuits, and waste-gas scavenging systems to minimize leaks of anesthetic gases into the operating rooms.
  • Train all workers in hazard awareness, prevention, and control of exposures to waste anesthetic gases.
  • Develop a monitoring program supervised by a knowledgeable person in every operating facility. Such a program should include quantitatively evaluating the effectiveness of a waste-gas control system and repeatedly measuring concentrations of anesthetic gas in the breathing zones of the most heavily exposed workers while they perform their usual procedures.
  • Keep good records of all collected air sample results for at least 30 years.
  • Keep medical records of a worker's exposure for 30 years after his or her employment has ended (see 29 CFR 1910.1020 Access to Employee Exposure and Medical Records).
  • Obtain baseline liver and kidney data for operating room personnel and monitor their liver and kidney functions periodically.
  • Record medical histories for workers and their families, including occupational histories and outcomes of all pregnancies of female workers and wives of male workers (if possible).

(Editor's note: The NIOSH document is available at


1. Centers for Disease Control and Prevention. Request for information on waste halogenated anesthetic agents: Isoflurane, desflurane, and sevoflurane. 71 Fed Reg 8,859-8,860 (Feb. 21, 2006).