The CDC, which conducted its survey in 2003 but released it on Thursday, said it was the first study to offer a state-by-state look at the prevalence of smoking in American homes.
The highest number of houses that banned smoking was found in Utah, with people in nearly nine out of 10 homes saying smoking was never allowed. However, the federal agency contributed the statistics to state's large population of Mormons, who eschew tobacco.
Kentucky took the lowest place where nearly more than half of households didn't allow smoking inside the house and made it a rule to send them outside or, at least, to the garage.
AP quotes Dr. Corinne Husten, co-author of the study and chief of the epidemiology branch of the CDC's Office on Smoking and Health, as saying, "That really says that people are starting to understand the hazards of second hand smoke."
The CDC report covered 127,000 U.S. households in 2003, the most recent year for which such data was available. The study looked at 900 to 7,000 homes in each state. Similar numbers were surveyed in previous years.
It was found that the household which had at least one smoker, nearly 32 percent of people were asked to smoke outside in 2003. The figure was barely 10 percent in 1999. Among households with no smokers, the percentage with such rules rose from 57 percent to almost 84 percent.
The CDC attributes the dramatic increase to scientific reports and other information in the last 15 years warning that passive smoke causes premature death and disease. The study was published the CDC's Morbidity and Mortality Weekly Report.
