Dental workers are exposed to Nitrous Oxide (N2O) during administration of this anesthetic gas to patients. Exposures should be minimized to prevent short-term behavioral and long-term reproductive health effects that can be produced by N2O.
NIOSH research has shown controls including System Maintenance, Ventilation and Work Practices can effectively reduce N2O concentrations in dental operations to approximately 25 ppm during analgesia administration, the exposure limit recommended by NIOSH. Uncontrolled exposures to N2O have exceeded 1000 ppm. Three methods of control are recommended:
The principal contributors to this HAZARD CONTROLS are James D. McGlothin, Division of Physical Sciences and Engineerfing, and Barbara L. Dames and Jerome P. Flesch, Education and Information Division, NIOSH.
|This document is in the public domain and may be freely copied or reprinted. NIOSH encourages all readers of this HAZARD CONTROLS to make it available to all interested employers and workers.|
DHHS (NIOSH) Publication No. 96-107
STEP BY STEP APPROACH FOR CONTROLLING N2O
|1||Visually inspect all N2O equipment (reservoir bag, hoses, mask,connectors) for worn parts, cracks, holes, or tears.||Replace defective equipment and/or parts.|
|2||Turn on the N2O tank and check all high to low pressure connections for leaks. Use a non-oil-based soap worn solution to check for bubbles at high pressure connectors, or use a portable infrared gas analyzer.||Determine leak source and fix. If tank valve leaks, replace tank; if O-rings, gaskets, valves, hoses, or fittings, replace. Contact the manufacturer for parts tact the manufacturer for parts replacement. For threaded pipe fittings, use Teflon tape. Do not use this tape on compression fittings.|
|3||Select scavenging system and mask. Mask should come in various sizes to patients. Scavenging systems should operate at air flow rate of 45 lpm.||Provide a range of mask sizes for patients. Check to see that noise levels at the mask are acceptable when the scavenging system exhaust rate is operated at 45 lpm.|
|4||Connect mask to hose and turn on vacuum pump before turning on N2O. Scavenging system vacuum pump must have capacity to scavenge 45 lpm per dental operation.||Determine proper vacuum pump size for maintaining 45 lpm flowrates, especially when interconnected with other dental scavenging systems. If undersized, replace pump.|
|5||Place mask on patient and assure a good, comfortable fit. Make sure reservoir bag is not over or under inflated while the patient is breathing.||Secure mask with "slip" ring Secure mask with "slip" ring for "good activity" from patient breathing.|
|6||Check general ventilation for good room air mixing. Exhaust vents should not be close to air supply vents (use smoke tubes to observe air movement in room.)||If smoke from smoke tubes indicate room air mixing is poor, then increase the airflow or redesign. If exhaust vents are close to air supply vents, relocate (check with ventilation engineers to make adjustments).|
|7||Conduct personal sampling of dentist and dental assistant for N2O exposure. Use diffusive sampler or infrared gas analyzer (see sampling methods).||If personal exposures exceed 150 ppm during administration, improve mask fit and make sure it is secure over the patient's nose. Minimize patient talking while N2O is administered.|
|8||Repeat procedure in step 7.||If personal exposures are less than 150 ppm but greater than 25 ppm, implement auxiliary exhaust ventilation near the patient's mouth. Capture distance should no greater than 10 inches from the patient's nose and mouth area and exhaust no less than 250 cfm at the hood opening. Avoid getting between the auxiliary exhaust hood and patient's mouth and nose area.|
NIOSH recommends air sampling for N2O be conducted periodically to: (1) measure worker exposures to N2O during anesthetic administration Personal Sampling, and (2) control N2O leaks in the delivery, scavenging and ventilation systems Area Sampling. 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. Sampling methods available are summarized below.