Ten Harvard-affiliated hospitals have joined forces to make their facilities tobacco-free in an effort to encourage their employees and patients to quit or make a plan to quit smoking. The new policy comes as part of the American Cancer Society’s 36th annual Great American Smokeout, a yearly push to encourage America’s 45 million smokers to give up the habit.

Over the course of the next several months, employees, patients, and visitors of these Boston-area hospitals will begin to see signs that prohibit smoking throughout hospitals’ campuses and facilities.

Smoking rates have declined since 1965, when 42 percent of Americans were reported as smokers. Since then, widespread efforts to decrease the number of smokers have had an impact, but since 1990 the incidence has plateaued at around 20 percent.

Brigham and Women’s Hospital plans to adjust its existing program to encourage inpatients to quit smoking, and will also develop a program to help support employees who wish to quit smoking. They also plan to develop strategies for sharing information about free or low-cost resources for quitting smoking.

“As a hospital it is imperative that we provide a healthy environment for our employees, our patients and our visitors. Many of our patients are extremely vulnerable when they come to us, and we need to do everything we can to protect them,” Brigham and Women’s Hospital President Dr. Elizabeth G. Nabel said in a statement.

Some hospitals, such as Saint Anne’s Hospital, have been smoke-free since July. Saint Anne’s has eliminated outdoor smoking areas and prohibited tobacco products on all properties that are owned or leased by the hospital—even extending to inside of cars parked on hospital properties, according to a statement issued by the hospital.

Tobacco products are defined to include cigarettes, cigars, smokeless tobacco and electronic cigarettes. The policy seeks to reduce the health costs associated with tobacco-related illnesses, according to a statement by Saint Anne’s President Craig Jesiolowski.

“In terms of death, health conditions, lost work days, and increases in insurance premiums, smoking is the number one preventable behavior that we can positively impact,” Jesiolowski said.