An important point to reflect on is that here will always be one person on staff who will be running to the administration to report what is being said or done. Keep that in mind before you rant and rave in the staff room. I would suggest you keep most negative comments to yourself. Condemning, complaining, and criticising doesn't result in much except making you look bad. Occasionally you will have no choice but to miss part or all of a meeting.
Emergencies do arise.
Still, it is good protocol to let your department head or principal know ahead of time that you will be absent. There should be an excellent reason. Nothing is more exasperating than booking out audio-visual equipment only to find it has been removed when you need it. If equipment has been booked for that period and day, you have no business removing it simply because you did not plan ahead. Removing equipment without booking is another fault.