The study examines the concentrations of nitrous oxide that are achieved in blood, exhaled air, and urine after three different exposures to nitrous oxide:

inhalation of three or four cartridges of nitrous oxide released in a car cabin in a switched-off car, consumption of 100 g of whipped cream in which nitrous oxide is used as a propellant, and exposure through work as a midwife in a delivery room.

The concentrations in blood and exhaled air are measured for up to 1 hour after exposure, and in urine for up to 2 hours after exposure. The concentrations in blood and urine are measued with gas chromatography and mass spectrometry, while the concentration in exhaled air is measured by a sensor using an NDIR sensor (Olythe, France).

For arm 1, 2, and 3:

Inclusion Criteria:

• Age 18-65 years
• Able to understand Danish
• Willing to use effective contraception for 24 hours after the end of exposure (oral contraceptives, contraceptive implant, transdermal patch, vaginal ring, or injectable contraceptives)
• Written informed consent

Exclusion Criteria:

• Current or past abuse of drugs, nitrous oxide (N₂O), or alcohol
• A psychiatric disorder requiring medical treatment, including severe depression
• A diagnosis of epilepsy
• Symptoms of peripheral neuropathy
• Significant cardiac or pulmonary disease
• Previous allergic or adverse reaction to N₂O
• Diving within the past 2 days
• Inability to refrain from diving for 2 days after the study
• Occupational exposure to N₂O
• Use of N₂O within the past 3 months
• Treatment with methotrexate, benzodiazepines, opioids, or other centrally depressant drugs
• Recent intraocular gas injection
• Known impaired liver or kidney function
• Pregnant or breastfeeding women (fertile women, defined as amenorrhea for less than 12 months, must have a negative hCG pregnancy test prior to receiving the study intervention)