Participants will breath 3 hours during daytime with a nasal mask under three different humidity modes (No humidity, controlled heated humidification, controlled heated humidification with heated tubing) with CPAP 8 and 12 mmHg and with and without leakage. The ambient room temperature is controlled with air conditioning. Changes in temperature and humidity is measured inside of the mask with a humidity sensor and recorded. After each phase the participants subjective opinion about humidity and temperature is asked.