Only green fireworks can be burst during a two-hour window each on Thursday and Friday, when Diwali revellers are allowed to light firecrackers.

The permissible noise level of firecrackers is 125 decibel at 4m from the source, said an official of the state pollution control board (PCB). The permissible level was 90 decibel at 5m from the source till the state government changed it through an order issued on October 17, 2023.

The change conforms to the national norms.

Multiple mobile phone apps can track the ambient noise level.

Calcutta was decked out in lights on Diwali-eve. A drive across the city also suggested frequent violations of the firecracker norms.

Camac Street, Rawdon Street and Ballygunge Circular Road, dotted with high-rises, were among the stretches that were noisier than the rest of the city.

A Metro lowdown on what is allowed and what is notand where to seek redress for violations:

When can green firecrackers be burst?

From 8pm to 10pm on Thursday and Friday, said Biswajit Mukherjee, former chief law officer of the PCB.

The norm is in keeping with a Supreme Court order, later reiterated by Calcutta High Court and subsequently turned into a directive by the PCB. After 10pm, there is a ban on all fireworks, irrespective of whether they emit sound or only light, Mukherjee said.

How can a green firecracker be identified?

The only way to identify a green firecracker is by scanning the QR code on the box. Any scanner can be used for this.

On scanning the code, a certificate should be generated mentioning the name and nature of the fireworks, details like the name and address of the manufacturer, chemical composition of the fireworks and the percentage of reduction in emission, a police officer said.

The certificate should be on the letterhead of the Council of the Scientific and Industrial Research (CSIR)-National Environmental Engineering Research Institute (NEERI) and should bear the official seal of the authorised signatory of the CSIR-NEERI.

NEERI has been mandated to look into the technical aspects of the green fireworks, including formulation, verification and training for firework manufacturers.

What is a green cracker?

The NEERI website mentions that green crackers are “made with reduction in size of shell, elimination of ash usage etc., reduced usage of raw materials in the compositions, of uniform acceptable quality, and/or use of additives as dust suppressants to reduce emissions”.

It adds that these fireworks ensure at least a 30 per cent reduction in the emission of particulate matter.

Can I be punished if I violate the norms?

A person found bursting a banned cracker can be prosecuted under the Explosives Substances Act. “If found guilty, the person can be imprisoned for up to three years,” said a police officer.

If anyone is found bursting crackers beyond the stipulated hours, the person “can be imprisoned for up to six months,” said the officer.

The Explosives Substances Act can be invoked if the person is found bursting a banned cracker.

Special instructions have been given to officers to maintain vigil on high-rises and the outskirts, from where the maximum number of violations of the firecracker ban is usually reported on Diwali.

Where can I complain if the orders are not followed?

Complaints can be lodged with the police or the state pollution control board.

Emergency phone numbers:

• Kolkata Police control room: 22143230
• Kolkata Police traffic control room: 22143644
• Bidhannagar commissionerate control room: 23358788
• Howrah City Police control room: 26374761, 26374762, 26415614
• Barrackpore City Police control room: 25932647, 25455030
• Emergency helpline: 100
• Fire brigade control room: 22861570, 22521165
• State pollution control board control room: 22023057, 18003453390 (these numbers will be functional from 5pm till midnight on Thursday, and again from 5pm till 10pm on Friday)

Is it going to rain on Diwali?

Most likely. But the rain is not going to be heavy, the Met office has said. The forecast is for a partly cloudy sky, with one or more spells of light rain.

“An anticyclonic system persists in the lower level of the atmosphere over the Bay of Bengal. Moisture incursion from the Bay and some local moisture are combining to form the clouds over Calcutta and other coastal pockets of south Bengal,” said a Met official.

The maximum and minimum temperatures are likely to be around 31 and 25 degrees Celsius, according to the Met forecast.

Will there be special Metro services on Diwali?

There will be special night trains between Kavi Subhash (New Garia) and Dakshineswar. From Kavi Subhash (New Garia), the last four Dakshineswar-bound trains will leave at 10pm, 10.20pm, 10.40pm and 11pm. From Dakshineswar, the last four New Garia-bound trains will leave at 9.48pm, 10.08pm, 10.28pm and 10.48pm.

“The night trains will help devotees headed for Kalighat and Dakshineswar,” said an official.