Health and Safety issue on BA Comair planes

I flew to dbn and back from Ortia on BA, on both flights we had to sit on the plane for 30 mins before the engines started. There are NO air vents on these planes so for 30 mins we sat in a claustrophobic plane, temps of approximately 28 degrees. It was unbearable. I couldn't breathe. On the BA flight back I asked the air hostess why there was no air and she said it will come on when the engines start, I told her I was going to complain and she said go ahead they have complained millions of times. Clearly this is an issue that is not only bothering clients but staff alike. If a Health and Safety officer was to check the temp, and lack of air I am sure they would find it lacking. There must be a viable solution to ensure the safety of staff and passengers. If I have to fly BA again I will only enter the plane when all the passengers are on, as this seems to be the only current solution.