[Marttt]

need more info, we don't even know which entity classname are you using, you mentioned env_smokestack, but without more code is just a guess
and you code btw you are reseting the alpha everytime to "0" in the else clause, and I hope is just a snippet code, otherwise [2000] array is not enough, sometimes the (network) entities created may be between 1~2048 in L4D2