I used to work at a gas station, and it was instilled in all the workers that the air pump (for tires) was extremely dangerous. Even a small change in air pressure would burst our eardrums. That being said, why do our eardrums remain intact even when we slam our car doors?
It takes quite a bit of pressure for eardrums to burst, actually.
While SCUBA diving, your ears will only start hurting in worrying ways when you reach ~10 meters, which according to my calculations is about twice the atmospheric pressure. Converted to PSIs, rounding up a lot along the way, I get 30. Don’t know the exact pressure for actual ear damage to happen, but slamming your car door certainly doesn’t compress the air inside it by a factor of two, much less something that would actually damage your eardrums.
On the other hand, compressed air pumps push out between 150 and 300 PSIs according to Google-Fu. Which is to say, between 10 and 20 atmospheres’ worth of pressure, or the equivalent of a 200 meter dive. Incidentally, that would be the crush depth of a WW2 submarine. That’ll do the job.
I wasn’t aware bursting your eardrums would prove immediatly fatal? Surly this would make “flashbangs” a less than desirable choice for a less-lethal weapon?
It may not qualify as “bursting”, but I had an eardrum rupture due to an ear infection, and not only did I not die, it healed without problem or hearing loss. In fact, the moment it ruptured is a moment I look back on very fondly: it made the pain stop.
I suspect there is a bit of misunderstanding here. Compressed air sources are indeed extremely dangerous, but what is a small delta in air pressure for an air pump is a very large change for the human body. One suspects that the warning was to prevent idiotic behaviour amongst the workers. One could easily imagine someone deciding one boring afternoon that it would be a great joke to sneak up behind a workmate and startle them with the whoosh of air from a tyre inflator. Sure, and it will blow their eardrum without even noticing it was there, incudling lots of concomittant damage on the way. Similarly, any other bodily orifice (it doesn’t bear thinking about what some bored lads will get up to.) At close range the air source is capable of piercing the skin and inflating the body - a fatal embolisim isn’t hard - or other devastating injuries. Even using an air source to dust yourself down after working on something messy is potentially fatal.
The other obvious danger is overinflating a tyre. A rupturing tyre can kill.
I thought your Eustachian tubes were there to equalize air pressure, and that only a very dramatic and sudden pressure change would blow out your eardrum before the pressure had a chance to equalize. Don’t the Eustachian tubes mitigate any pressure issues from normal diving, etc.?
One of my HS shop teacher’s first day speeches was about how air compressors and intestines don’t mix well.
You can get pain from unequalized middle ears long before you reach 10 meters, if you’ve got a blocked Eustachian or don’t equalize on the way down.
Eustachian tubes can be blocked by mucus, or just get stuck shut for no particular reason. And if the pressure difference gets too large, the pressure actually tends to keep them shut. Hence things like the Vasalva maneuver, and other tricks divers use to equalize their ears as they submerge. The Eustachian tubes evolved for fairly gradual pressure changes, not doubling the ambient pressure in 60 seconds.
Well, yes. Sorry if I was being my usual opaque self, but I was talking about diving without equalizing. If you do equalize, you’re not gonna burst your eardrums or feel any pain for that matter, since it’s the pressure differential that does that. Equalizing eliminates the pressure dif, as you said.