New Magic Item: Chain Mail of Gaseous Skulduggery

This is my last entry into the OSR Superstar contest.  "Gaseous Skulduggery" kind of sounds like something I do in the bathroom, though....

Chain Mail of Gaseous Skulduggery

This suit of typical-looking chain mail provides the wearer with a strange ability.  Once per day the wearer may invoke the power of the armor, which is to make the wearer gaseous immediately for 1d4 rounds.  In gaseous form the wearer cannot manipulate the physical world, so all equipment falls to the ground, except for the armor and one weapon chosen at the time of the power’s invocation, which turns gaseous like the wearer and returns to solid form along with the character.  A gaseous character may pass through cracks in walls, through holes, and through other areas too small for his body to fit, as well as over walls and other barriers. He gains a flying speed of 9 while transformed.  The character is immune to physical attacks of all kinds during the time he is in this form, but a forceful wind or similar effect will cause the character 2d6 points of damage as his form is pulled apart temporarily, not to mention falling from height if he chose to fly upward while gaseous.  The Referee should roll the duration of the change in secret and not reveal how long the transformation will last.