However, US embassy sources said that the embassy has been using air purifiers for a long time and claimed, in turn, that this had nothing to do with the presidential visit. The sources said that the embassy uses the purifiers to purify the air through the air-condition ducts.

The US had, in October last year, termed as “very unhealthy” the air quality level in the national capital, which could result in significant aggravation of heart or lung diseases. The US embassy in New Delhi had earlier reportedly established an air quality monitoring programme with on-site measuring instruments, and had then said the Air Quality Index value 260 falls in the category of “very unhealthy.” The 260 AQI was a measure based on the amount of fine particulate or PM 2.5 in the air, a standard recognised by the US Environmental Protection Agency and which allows the comparison against US standard measures.

The category had defined “significant aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly, significant increase in respiratory effects in general population” as resultant health effects.

The US warning had then come with a cautionary statement that “people with heart or lung disease, older adults, and children should avoid all physical activity outdoors and that everyone else should avoid prolonged or heavy exertion.”