The gas was heavier than air by design so it would sink down into the trenches.Since the dogs didnt have protective foot wear they would be subject to the burns shown in the picture above.
BTW Masonz,the Rottie wasnt around during roman times despite what you may have heard,however they are from the line on Mollosors which were the type of dogs the Romans used. The Rottie is a mastiff's breed that was used mostly to pull carts,like the butcher's cart or ice cart.this is why they are sometimes called the Butchers dog.
