Alternatively, strips of cassette or video tape about 15 cm (6 in) long can be hung from the ceiling every
1-1.5 m (3-5 ft). These should be positioned in front of an air inlet near the entrance to the house up to the
apex of the house. When the fans are on, every strip of tape should move, including the one closest to the
roof apex. The tape closest to the inlet should show significant movement, and will blow strongly against the
roof. Movement of the tapes should get less the closer the tape is to the roof apex. The last tape (in the apex
of the roof) should only move gently showing that the air has just made it to the middle of the house and has
stopped and started to move downward. These tapes can remain in place throughout the production cycle
and provide a quick visual check when entering the house.