This is very important when it comes to a secondary coat of Flower Wall Stickers, because, like you, your house breathes. If it is an older house particularly, the exchange of air may happen in as few as five minutes, though even in newer homes, the exchange may be 15 to 20 minutes due to the “breathing” your home does.In this breathing process, your house sucks in the same air you do from the outside air, although some of the nasty stuff gets filtered out in your air conditioning unit or your furnace filtration system, but a lot of it floats through your house and sticks to your walls. When this happens, over time, it creates a surface that doesn’t hold wall stickers as well as you’d like it to. So, that’s why you need to wash the walls with TSP before you wall stickers. Wall Stickers at beat quality at WallStickerDeal.com