1. Occupational Exposure to Nitrous Oxide
Presented by the Office of Environmental
Health and Safety
Welcome to the Occupational Exposure to Nitrous Oxide on-line training presented by the Office of Environmental Health and Safety. This presentation is best viewed in Internet Explorer. After the presentation has concluded, you may review the slides to complete the quiz. The quiz can be completed online.

2. Uses of Nitrous Oxide
Anesthetic agent in medical, dental, and veterinary operatories
Food processing propellant
Component of certain rocket fuels
Oxidant for organic compounds
Nitrating agent for alkali metals
Nitrous oxide is routinely used in operatories as an anesthetic agent due to its painkilling, numbing and relaxing effects. Approximately 35% of all dentists use nitrous oxide to control pain and relieve anxiety in their patients.

3. Chemical Description
Synonyms: laughing gas, factitious air, nitrogen oxide, dinitrogen monoxide
Chemical formula: N2O
Clear, colorless gas at room
temperature
Slightly sweet odor and taste
Nitrous oxide is commonly known as laughing gas. It is a colorless gas with a sweet odor and taste.

4. Routes of Exposure
Exposure to nitrous oxide occurs primarily through inhalation.
Skin exposure to liquefied gas may occur when handling compressed gas cylinders. This is a result of the rapid evaporation of the liquefied gas.
Nitrous oxide exposure in operatories occurs primarily through inhalation. However, when handling compressed gas cylinders, skin exposure to the liquefied gas may occur.

5. Health Effects
Acute: dizziness, slurred speech, difficulty breathing, headache, nausea, fatigue, irritability
Chronic: tingling and numbness; difficulty concentrating; interference with gait; reproductive effects; neurologic, renal, and kidney disease
Pure nitrous oxide will result in asphyxiation.
Cryonic burns may occur when handling compressed gas cylinder.
Inhalation of nitrous oxide will cause a variety of central nervous system effects, including dizziness, headache, slurred speech, and irritability. If chronically overexposed, nitrous oxide may cause tingling and numbness, reproductive effects, as well as neurologic, kidney, and renal disease. Inhalation of pure nitrous oxide will result in asphyxiation. When skin is exposed to the liquefied gas from compressed gas cylinders, cryonic burns, commonly known as frostbite, will occur.

6. How EH&S Monitors Exposure
An Assay Technology ChemDisk monitor for nitrous oxide is worn for the duration of the procedure on the lapel to represent the breathing zone.
The disk is collected and sent to
an AIHA accredited laboratory
for testing.
A report of the results is
distributed to the supervisor
and the employee.
EH&S uses a ChemDisk monitor for nitrous oxide to measure employee exposure levels. The disk is worn on the lapel to represent the breathing zone of the employee and is worn for the duration of the dental procedure. The disk is then sent to an accredited laboratory for analysis. A written report of the results as well as recommendations to reduce employee exposure are distributed to the employee and supervisor.

7. Employee Exposure to Nitrous Oxide
OSHA does not regulate nitrous oxide exposure.
ACGIH TLV: 50 ppm as a TWA
EH&S compares your exposure to the ACGIH TLV.
According to the American Conference of Governmental Industrial Hygienists, employees should not be exposed to more than 50 ppm of nitrous oxide as a time weighted average. The Occupational Safety and Health Administration does not regulate nitrous oxide exposure.

8. ACGIH TLV TWA
ACGIH Threshold Limit Value is the average concentration for a normal 8-hour workday and a 40-hour workweek to which nearly all workers may be exposed repeatedly, day after day, without adverse effects.
EH&S uses exposure limits set by the American Conference of Governmental Industrial Hygienists. ACGIH reviews employee exposure limits annually. The TLV is the average concentration to which one can be exposed repeatedly for a normal 8-hour workday without any adverse health effects.

9. When Will Monitoring Take Place?
Initial monitoring.
Annual monitoring.
Periodic monitoring when initial results are above the TLV or there is a change in the procedure.
EH&S will continue to monitor employee exposure annually unless your exposure exceeds the ACGIH TLV or there is a change in your work procedure.

10. Protective Work Clothing and Equipment
Scavenging system provides adequate respiratory protection when operating within design specifications.
Thermal resistant gloves are necessary when handling compressed gas cylinders, as this may present a cryogenic hazard.
When working with the anesthetic gas, protective clothing and eye protection are not required. When at the proper flow rate, the scavenging system should provide adequate protection. When handling compressed gas cylinders, thermal resistant gloves should be worn to protect the skin.

11. Leaks
Stop the leak (shut off cylinder) if it is possible to do so without risk.
Provide additional ventilation to the area.
Isolate the area until gas has dispersed.
In the case of a leak, shut off the cylinder if you are able to do so without risk. Provide additional ventilation and isolate the area until the gas has dispersed.

12. Storage Cylinders should be secured with straps or chains to prevent
physical damage.
For additional storage information, visit
Compressed gas cylinders should be stored in the upright position and secured with straps or chains to prevent falling, tipping or rolling. You can visit the EH&S compressed gas safety web page for additional information.

13. Control Measures for Anesthetic Delivery System
Check all rubber hoses, connections, tubing, and breathing bags.
Check both high and low pressure connections.
Check nitrous oxide and oxygen mixing system.
Perform leak testing of the equipment.
There are several ways to control exposure from the delivery system, including visual inspections of all hoses, tubing, connections, and the mixing system. Leak testing of equipment with a soap solution should also be performed. All parts should be replaced when damaged or recommended by the manufacturer.

14. Control Measures for Scavenging System
Assure that the nitrous oxide is turned on only if the scavenging system is also activated.
Scavenging systems use local exhaust ventilation to collect waste gases from anesthetic breathing systems and remove them from the workplace. Always be sure the scavenging system is activated before turning on the nitrous oxide delivery system. This can be guaranteed by using an automatic interlock system.

15. Control Measures for Scavenging System
Scavenging system exhaust rates should be approximately 45 L/min,
regardless of the number
of systems operating at a
time.
Monitor flow rate with a
flowmeter.
Regardless of the number of systems in use at a time, the scavenging system flow rates should always be at least 45 L/min. This minimizes leakage around the mask. Flow meters, as seen in the picture, can monitor the flow rates.

16. Control Measures for Scavenging System
Supply scavenging mask in a variety of sizes to ensure a secure fit over the patients nose or face.
All scavenging pumps should
vent to the outside of the
building away from fresh
air intakes, windows, and
walkways.
Various sizes of scavenging masks will allow you to have a proper fit over the patient’s nose to minimize leaking. All scavenging pumps should vent to the outside to prevent exposing others to nitrous oxide.

17. Work Practices to Control Exposure
Do not fill the breathing bag to capacity with nitrous oxide.
Minimize speech and
mouth breathing by the
patient during the procedure.
After the procedure, flush
the system of nitrous oxide.
There are several work practices you can do to minimize your exposure. First, do not over inflate the breathing bag with nitrous oxide; this will cause excessive leakage from the scavenging system. Second, it is extremely important to minimize mouth breathing and speech by the patient. Last, the system should be flushed after the procedure is complete. This can be accomplished by administering oxygen to the patient through the anesthetic system for 3 to 5 minutes.

18. Contact Information
For additional information, please contact EH&S at (252) , visit our website at or visit our office located at 210 East 4th Street.
Send completed quiz via
or mail to EH&S to receive credit.
Click the link to complete the QUIZ
For additional information, please contact the Office of Environmental Health and Safety via telephone, , or visit our office on 4th street. Remember to send your completed quiz to EH&S to receive credit.