One thing about the show that doesn't come up much is that they actually test much more than we see. They've shown this in the DVD commentary and some special episodes.
This doesn't mean I agree with everything they've said. And sometimes logic seems lost on them. Some verdicts annoy me because I find they've missed an important element.
An example is the straw through a palm tree episode where, instead of using the tiny surface area of a single straw they sent down a bundle. Or that a rifle round that was set off by accident probably wouldn't really hurt because it didn't mark up a crash test dummy, though it made a hole in his pants. Or the infamous chicken cannon one.
To their credit, they do 'revisit' episodes now and then, and have changed their verdict after fans corrected them on their methods.
BTW: Confirmed/plausible myths include:
The chicken cannon (an accident involving using a frozen chicken in a bird-strike test for a train)
Gas cylinder rocket
Exploding water in a microwave
Certain submerging car myths
Exploding pants (partial confirmed, as the fertilizer caused pants to burn extremely quickly, not explode)
Rifle round used as a temporary headlight fuse going off and injuring driver.
Bullets fired into the air returning with lethal velocity (both busted and confirmed as they found that a bullet fired straight up is non-lethal, but at about 80 degrees or so it returns lethal.)
A shotgun (slug) can take out a lock
Weather balloon armchair flight.
Eyepatch nightvision (plausible due to no historic evidence they could find)
Steel-toed boots being safer than not
And I'm sure there are others, but I can't remember them.
The point is that it's a fun show overall. One of the hosts even let slip that it's in his contract to have at least one explosion per episode. The people, while well trained and very smart, aren't experts in all fields and the myths they test are urban legends that fans want to see.