Dear , as u said u are a passive smoker so first u try to avoid company and surrounding place of that smoker. First important think is u should not get exposed to smoke . Avoid tat first important thing. Second thing , there is nothing called as cleaning lungs , u can do Pranayama like anulom vilom which wl help u. U can do excercise of lung.. Called as incentive spirometry but with consultation only .u have to consult once pulmonogist . Prevention is better than cure so before u get any problems u Consult doctor

Take appointment for medications and diet lifestyle correction to decrease effects of passive smoking. Pranayam anulom vilom will be beneficial Practising deep long breathings regularly will be beneficial