Identify leaking pads on your woodwind instrument easily with this step by step guide.
Check for clarinet or flute air leaks by taking the instrument apart, cupping the ends of the instrument, closing all finger and pad openings, and blowing air through. The instrument’s pads and springs should resist heavy air flow. If you feel or hear even the slightest of leaks and are not sure, have a friend help you by putting their hand away from your clarinet and feeling.
Note that if a large amount of air or light leaks through, it may not be a leak, but rather an adjustment problem. A spring is not taut enough or something is bent enough to create a problem. With woodwinds, cork placement means everything, so there is always a chance some cork is just worn and isn't doing its job any more.