Firefighters are to be studied in an attempt to understand how the heart is affected by their type of work.
Scientists will follow them during training as they tackle fires which can be as hot as 700C.
Firefighters are more likely to have a heart attack on duty than at other times, said the British Heart Foundation (BHF) which has provided £187,000 towards the research.
Researchers at the University of Edinburgh will look at possible reasons why this occurs, such as the combination of heat and different stresses put on the body when fighting flames.
They will take measurements of the heart and blood vessels of Lothian and Borders Fire and Rescue Service crew before they tackle a blaze at their Edinburgh training facility.
Dr Helene Wilson, research adviser at the BHF, said: "We can't be sure exactly what the effects of air pollution are on the heart, particularly at the low levels we find in most UK cities. But there is convincing evidence that even low levels of air pollution might be bad for the heart.
"At higher levels, like those faced by firefighters, for example, or in developing cities like Beijing, pollutants are likely to have a more serious and long-lasting effect. This project will help bring us closer to working out the reasons why pollutants can have such a harmful effect on heart health."
Dr Nick Mills, the consultant cardiologist leading the research, said: "We know that air pollution, especially the particles in diesel exhaust, can have a long-lasting effect on the heart and circulation. Firefighters on duty are faced with air pollution at extreme levels which actually may be a greater risk to their health than the fires they are tackling.
"Firefighting puts stress on the heart in lots of different ways, so we can't be sure what causes the increased risk of heart attack but we know the risk is there. Hopefully this project will lead to further improvements in safety for firefighters who are risking their lives in the line of duty."
David Mackie of Lothian and Borders Fire and Rescue said: "Being in a fire can put stresses on the body in all sorts of ways, not least on the heart. We are very pleased to be working with University of Edinburgh scientists to try to understand the effect of tackling fires on the heart. Hopefully it can lead us closer to finding ways of managing the risk or even finding new equipment that can make firefighting safer."