Another CE duration query

[Tom Carman]

I made a character armed with a black-powder machine gun, and added this linked effect: Clouds of Smoke Change Environment 2" radius w/-2 OCV, No Range, Zero END, Personal Immunity. The idea was that it would be harder to target him in the smoke. The issue hasn't come up, but: how long should this no-END-cost effect linger?

[Steve Long]

You've clearly identified and delineated the special effect, so that gives you the answer: as long as the character keeps firing the gun. Some research, experience, or a decent guess should be enough to come up with a good answer as to how long the smoke cloud lingers. For example, one possibility might be "the Phase in which the gun is fired, +1 Segment." (At that rate, though, Continuing Charges might be better than 0 END.)