Delhi Pollution Control Committee recently floated a global tender for hand-held air pollution monitoring devices, which scientists hope would come before the plan kicks in. The major change in the scheme this time would be in the way monitoring is done and the locations selected, officials said.

Between January 1and 15, Delhi government had collected air quality readings from more than 180 locations around the city but compared them with the city's average levels in the previous year and sometimes with 2014 levels. Even though the government claimed there was consistent decline in PM 2.5 and PM 10 levels, the same wasn't reflected in the data recorded by the fixed ambient air quality monitoring stations. Weather had also played havoc as there was western disturbance that led to the peaking of air pollution levels on certain days. Overall, the minor improvement in air quality due to the scheme couldn't be captured properly during the phase.

"We had to issue a global expression of interest because we weren't sure if these devices are available in India. You cannot establish permanent monitoring stations everywhere so it's easier if we have some equally efficient mobile devices. We aren't sure if the devices will be available for odd-even monitoring," said a senior official in the environment department, adding that the experience of the first leg is being analysed to see how the monitoring can be made effective.

The department is also planning to rope in a private laboratory to monitor air quality at specific locations. "We involved a private lab last time also since the monitoring was conducted in different locations. But the methodology will be changed drastically this time, focusing only on a few locations and comparing levels before and after the scheme starts," the official added.

Internally, there are some who also believe that the government should focus on monitoring and results more. "We know from last year's experience that the benefits are very difficult to capture because every day is different and meteorology influences results a lot. People understand that it has benefits," said an official who declined to be quoted. Delhi government will not be releasing any analysis on ozone levels though.