turning off oxygen
flow to the patient:
8% A, 7% P
vide training, proce-
dures, and policies
that will decrease the
risk of hazard to the
clinician. Many of
change the behavior of people, as opposed to removing the hazard (e.g., training
staff to check hosing and bag condition for leaks before turning the nitrous
oxide on for every patient). In the survey, 13% of respondents said that the
office did not have standard procedures to minimize worker exposure to
nitrous oxide. Three percent responded that they were not being trained
on safe handling and administration of nitrous oxide. Each of these acts
puts people at risk.
We all have a responsibility to our patients and to staff. Those
responsibilities should have engineering, administrative, and work practice
controls in place that address successful management of nitrous oxide
emissions, including properly fitted nasal scavenging masks; supplemental
LEV (when nitrous oxide levels cannot be adequately controlled using nasal
masks alone); adequate general ventilation; regular inspection of nitrous
oxide delivery and scavenging equipment for leaks; availability of standard
procedures to minimize exposure; periodic training; ambient air and
exposure monitoring; and medical surveillance.
3 These practices can and
do effectively reduce nitrous oxide levels in the dental setting to 25 ppm
during analgesia administration, which is the NIOSH standard.
5 It is
important to remember that, according to NIOSH,
5 uncontrolled exposures
have exceeded 1,000 ppm.
NIOSH supplies a great sheet you can post in your office to help you
remember what you should be doing to keep both you and the patient safe.
To find the related NIOSH Technical Data Sheet, go to cdc.gov/niosh/docs/
According to its website,
5 NIOSH recommends air sampling for N2O be
Sampling can be used to measure personal breathing zone exposures of
dental workers, and to detect leaks in the anesthetic delivery system, ineffective
capture by the scavenging system, reentry in the room ventilation system, and
circulation to other areas of the dental offices. RDH
1. Rowland AS, Baird DD, Weinberg CR, Shore DL, Shy CM, Wilcox AJ. Reduced fertility among
women employed as dental assistants exposed to high levels of nitrous oxide. N Engl J Med.
2. Howard WR. Nitrous oxide in the dental environment: Assessing the risk, reducing the exposure. J
Am Dent Assoc. 1997;128:356-360.
3. Anesthetic Gases: Guidelines for Workplace Exposures. United States Department of Labor
Occupational Safety and Health Administration website. https://www.osha.gov/dts/osta/anesthetic-
gases/#C1. Published July 20, 1999. Updated May 18, 2000. Accessed July 9, 2017.
4. Boiano JM, Steege AL, Sweeney MH. Exposure control practices for administering nitrous oxide:
A survey of dentists, dental hygienists, and dental assistants. J Occup Environ Hyg. 2017; 14( 6):409-
416. doi: 10.1080/15459624.2016.1269180.
work practice controls
The Occupational Safety and Health Ad-
ministration (OSHA), the employee regulato-
ry agency, gives the following work practice
• “Prior to first use each day of the N2O
machine and every time a gas cylinder is
changed, the low-pressure connections
should be tested for leaks. High-pres-
sure line connections should be tested
for leaks quarterly. A soap solution may
be used to test for leaks at connections.
Alternatively, a portable infrared spec-
trophotometer can be used to detect an
• Prior to first use each day, inspect all
N2O equipment (e.g., reservoir bag, tubing, mask, connectors) for worn parts,
cracks, holes, or tears. Replace as necessary.
• Connect mask to the tubing and turn
on vacuum pump. Verify appropriate
flow rate (i.e., up to 45 L/min or manu-
• A properly sized mask should be selected and placed on the patient. A good,
comfortable fit should be ensured. The
reservoir (breathing) bag should not be
over- or underinflated while the patient
is breathing oxygen (before administering N2O).
• Encourage the patient to minimize
talking, mouth breathing, and facial
movement while the mask is in place.
• During N2O administration, the reser-
voir bag should be periodically inspect-
ed for changes in tidal volume, and the
vacuum flow rate should be verified.
• On completing anesthetic administration and before removing the mask,
non-anesthetic gases/agents should be
delivered to the patient for a sufficient
time based on clinical assessment that
may vary from patient to patient. In this
way, both the patient and the system
will be purged of residual N2O. Do not
use an oxygen flush.” 3
Author’s note: To see the administrative
and engineering controls, go to osha.gov/
dts/osta/anestheticgases and scroll down to
Did you know?
Most nitrous oxide hoods/nosepieces are
either disposable single-use items (i.e., used
one time and disposed of, cannot be reprocessed) or they are to be cleaned and then
sterilized in the autoclave or sterilizer, not
just disinfected with a wipe or spray. Read
the instructions for use for your hood/nose-piece and follow them.