Complex sentence: Under ideal conditions of zero wind, the effectiveness of the air door is at its maximum, but in windy locations air doors cannot create a perfect seal, but are often used to reduce the amount of infiltration from an opening.
Split into simpler sentences: Under ideal conditions of zero wind, the effectiveness of the air door is at its maximum. In windy locations, air doors cannot create a perfect seal, but are often used to reduce the amount of infiltration from an opening.