Concentrations of Nitrous Oxide in Blood, Exhaled Air and Urine After Various Types of Exposure.

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)