Heaters in Party Tents

I rally on a regular basis and our centre are fortunate that we have our own party tent that goes out almost every weekend. The party tent is heated by 2 cabinet heaters and several of the small portable gas heaters usually supplied for use in awnings. Recently there has been a concern about the safety of these heaters as one of our members complained of a very bad headache after attending a function when the gas fires were on. It has to be said that the party tent is usually full of people and only one person has ever complained. We have always felt that there is adequate ventilation in the party tent as you can never seal it completely so there is always airflow. On health and safety grounds, we have been told we should not have a naked flame in a party tent as this could be dangerous. Indirect blown air heaters (which are extremely noisy at 73 decibels at 7 metres) have been suggested as an alternative but require 240v supply and diesel to operate. 240v is not usually available on a normal weekend rally where there is usually no EHU. What do other centres do to heat their party tents or large awnings? Is there an expert out there that can give us a balanced and sensible view as the Caravan Club are unable to provide us with any guidelines. Catalytic heaters have been suggested with the use of carbon monoxide alarms to ensure fumes are not an issue and this seems like a sensible solution. However they do not have a naked flame but do still run on gas. Your views would be very much appreciated.