I cannot say specifically, but the Otterbox is airtight and watertight. Part of DOT lighter case specifications include the ability to withstand a certain amount pressure difference due to altitude change.

Basically, (I believe) the box is supposed to hold sea level pressure even at high altitude so that the high altitude pressure (or lack thereof) doesn't suck your lighter fuel out of the lighter.

Also, the statement "As the only storage container complying with the DOT regulations…" on the Otterbox site is incorrect. Collibri also released a lighter case that meets DOT specifications.