"We all need to understand that N95 masks and air purifiers, whose sale has increased in the last few days due to pollution, may not provide full-time protection, and are not completely effective," said Mr Guleria, who is among the leading pulmonologists in the country.
N95 masks are respiratory devices that cover the nose and mouth.
Addressing media persons here after pollution rose to dangerous levels, Mr Guleria also hinted at nearly 30,000 anticipated deaths due to air pollution-related diseases in the Delhi-NCR.
"Once again, I want to warn that patients may die due to the current pollution levels... especially the ones who have respiratory issues. This is a silent killer," said Mr Guleria.
He said there was a 20 per cent surge in respiratory disease patients at the OPDs of the All India Institute of Medical Sciences.
"The most affected are children and the aged. Today's children witnessing such pollution will have serious implications in the next 20 years with their lungs getting affected badly," said Mr Guleria.