A 50% O₂/N₂O mixture is effectively used for its analgesic and anxiolytic properties in pain management of diverse short-term medical and superficial surgical procedures. However, healthcare workers are often exposed to high N₂O concentrations, exceeding the recommended limit (45mg/m³). Repeatedly occupational N₂O exposure might have adverse health effects.

To assess N₂O exposure levels of healthcare workers, using different delivery and scavenging systems, and discuss the available preventive measures.

Short-term (n=78) and long-term (n=38) atmospheric samples were collected near the breathing zone of healthcare workers during 50% O₂/N₂O mixture administration to patients. Seven different combinations of delivery/scavenging systems were used: single face mask, double face mask connected to a portable aspiration system, both with a demand or a classic valve, connected or not to a central waste gas scavenging system. INRS's method for N₂O sampling and analysis was used.

The single face mask was associated with N₂O exposure levels exceeding the recommended limit (83/89 (93%) samples>45mg/m³), including when a demand valve and/or central waste gas scavenging system were used (28/34 (82%)>45mg/m³). Single face mask-related N₂O values ranged between 17 and 4500 mg/m³ (median 400 mg/m³, IQR=160-1300). Procedures using the double face mask generated lower N₂O exposure levels (25/27 samples (93%)<45mg/m³); values ranged between 0.85 and 57 mg/m³ (median 14mg/m³, IQR=6-31).

Scavenger systems with high flow rate evacuation capacity are necessary to prevent healthcare workers from N₂O exposure. Information about risks and protective measures must be provided.