A study of the effects of passive smoking has been announced, as Northern Ireland prepares to introduce a ban on smoking in public places.
Smoking will be banned in workplaces from April
The Health Promotion Agency (HPA) wants to see how the ban affects the levels of passive smoking in 500 non-smokers who share a home with smokers.
The volunteers will be asked questions about their health before the new rules come in, and again in a year's time.
The prohibition of smoking in public places begins on 30 April.
The HPA commissioned researchers from Institute of Occupational Medicine in Edinburgh.
As well as questioning the volunteers, researchers will also measure amounts of nicotine in the air in 100 of the homes.
Dr Brian Gaffney, of the HPA, said there was conflicting evidence over what effects the ban would have.
"Some people say that smokers... may well end up smoking more at home - therefore exposing their families, who may be non-smokers, to increased levels of secondary smoke."
He said the research would help the HPA to work out who they should be targeting with information campaigns.
The HPA is asking anyone who wants to volunteer for the research to call 0800 023 2993.