Help Valve test Left 4 Dead 2’s latest campaign, unlock Dead Air

Valve updated the official Left 4 Dead blog today with a special request for the community. Valve’s in the process of finishing up the Cold Stream campaign, and so they’ve called on the community to pitch in by playing through the campaign and reporting any bugs they may find along the way.

As an incentive to help out, Valve has promised that if 20,000 players complete the campaign (and earn the achievement for doing so) by the end of this Sunday, they’ll go ahead and release the Left 4 Dead 2 conversion of Dead Air early – on July 22, to be specific.

To do your part, simply boot up Left 4 Dead 2 on Steam, select the campaign and play through it alone or with friends. As it happens, Left 4 Dead 2is on sale today for $4.99. If you haven’t picked it up already, now you have even more incentive to do so.