I had just emptied the drum on my 1 1/2 hp Grizzly, which has done a good job for me. I did not empty the refuse bag below the pleated filter. I turned the collector on an boom! Fortunately, the bag blew out on the side opposite me as I was right next to the machine. A cloud of dust and a hearty Hi, ho silver. My fault of course as I had not emptied that bag in to long. From the sound I thought it was the pleat. Happily, that was not the case. I was in the midst of a shop clean-up as I am beginning a new project, but I had just cleaned that side so well. I am the meathead of the day.