When the altimeter crown and the crown for setting the time are screwed down, the air pressure indication will only change significantly when the watch experiences changes in temperature, which affects the air pressure inside the watch. In other words, after putting the watch on at room temperature, the air pressure reading in the watch will increase as the temperature in the closed watch becomes higher and the pressure increases. When the watch cools down, the pressure will decrease and so will the pressure reading on the watch. When the altimeter crown is opened, the indicated air pressure will instantly adjust to the ambient air pressure. However, if the watch display behaves the same when the crown is screwed down (in position "0") as it does when the crown is in position "1", the watch is not tight and should be returned for inspection.