I had an Irish Red Ale with a starting gravity of 1.059 on Tuesday night, and pitched a pack of Nottingham right on the top and stirred it up.
Lucky my wife noticed the top bulging last night. The krausen had blocked the airlock, and the top probably would have blown off. It took me a few minutes to gently release the pressure, clean off the blockage and reinsert it. I looked a few minutes later, and the top was bulging again. At that rate, it was just futile to use the airlock. I just took it off and let the krausen out. This morning, I put the airlock back in, and it is still bubbling very actively, but I think it is safe now. Great dry yeast. I need a 10 gallon conical fermenter.