I just bought a FoodSaver and I noticed some bags not airtight. On experimenting, I found that if you make your own bag, inspect the first "weld"; sometimes the way you hold the bag in making this weld, it won't seal properly. For the second seal, if all the green lights don't light up, you may not have left enough material to stick in the inside chamber. Also, the food may have been too close to the cover and prevented it from going all the way down. Also, watch the cutting slide. Make sure it's all the way over to the left; if not, it may prevent a good seal. It's great if you watch what you're doing.