When there is a fresh-air vent for the house trap, if the outer end terminates on the outside of the foundation wall, the opening should be covered with a screen or perforated metal plate. The covering is needed to prevent children from stuffing toys, balls, or other objects into the opening and blocking air movement. Technically, an unprotected fresh-air vent opening is also a violation of the plumbing code. If you do not see a cover over the fresh-air inlet vent, record the fact on your worksheet as a reminder for later installation. You should also use your flashlight to determine if there is any blockage.
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