I am terribly sorry to hear this is happening. Wasps can be such a pain! This product is generally very good, was the whole air brick covered in the powder? The wasps will land on the air brick before entering the nest, which means they will carry the powder inside the nest. Is there also anywhere you can place the powder in the kitchen, on the floor boards, even under the floor boards? Please feel free to give us a ring and we can give you some advice. Thank you for your feedback.