How a cracker earns its green label: Inside the lab that tests Diwali smoke

The green label means reduced pollution, not zero pollution. A green cracker uses a specially designed chemical formulation that produces less smoke, dust and harmful gas than a conventional cracker of the same kind. This matters because even reduced emissions still enter the air people breathe.

Scientists compare the green cracker with a conventional version. It qualifies if it releases at least 30 per cent less particulate matter, or at least 20 per cent less particulate matter together with 10 per cent fewer gaseous pollutants. Particulate matter includes tiny dust and soot particles suspended after the burst.

The label therefore represents a measured result, not a visual claim. NEERI tests crackers in a controlled chamber and checks air pollution and noise. Green crackers can still be loud and smoky. The article notes that CSIR's SWAS crackers reach 105 to 110 decibels, so the label does not mean silent or harmless.

A controlled chamber creates the same enclosed conditions for every trial. This lets scientists compare one cracker fairly with a conventional cracker of the same type. Nothing escapes into the open air, and outside pollution does not disturb the readings.

After lighting the cracker, researchers collect particulate matter and sort it into PM10 and PM2.5 sizes. They measure gases such as sulphur dioxide in situ, meaning sensors detect them inside the chamber as they are released. A Level 1 sound meter records the sudden bang across the microsecond-to-seconds range.

The measurements are combined into an emissions and noise profile. Scientists then compare the result with the conventional version. Dr R J Krupadam says testing each firecracker sample for air pollution and noise takes approximately four hours. The method tests both visible smoke and invisible gases, while also capturing the brief explosion accurately.

The green standard is based on measured reductions against a conventional cracker of the same kind. This comparison matters because different cracker designs may naturally release different amounts of smoke and gas. The label is awarded only when a recipe meets one of the stated emissions thresholds.

The first route requires at least 30 per cent less particulate matter. The second requires at least 20 per cent less particulate matter along with 10 per cent fewer gaseous pollutants. Particulate matter means the tiny dust and soot particles left hanging in the air after a cracker bursts.

These limits do not make the cracker pollution-free. They set a lower-emission benchmark that laboratories can check in controlled conditions. NEERI measures PM10 and PM2.5, along with gases such as sulphur dioxide, then compares the results with a conventional product. The recipe either meets the numerical bar or fails it.

Breathing cracker pollution exposes people to both particles and gases. The article explains that PM10 particles are smaller than 10 micrometres, while PM2.5 particles are smaller than 2.5 micrometres. Because PM2.5 is much smaller, it can travel deeper into the lungs, which is why these particle sizes matter most to health.

The smoke also contains gases. Sulphur dioxide forms when sulphur in cracker powder burns, and scientists measure it inside the chamber. In general, inhaling particulate matter and irritating gases can worsen breathing problems and inflame the airways; these broader health effects are established knowledge, while the article itself does not list specific diseases.

Lower emissions reduce exposure, but green crackers are not pollution-free. Their standard requires measured reductions compared with conventional crackers. The article therefore supports a clear conclusion: less smoke and gas is preferable, but people can still breathe pollutants when these crackers are used.

Firework colours come from metals. When a metal compound is heated in a flame, its atoms absorb energy and release it as light of a particular colour. Barium compounds produce green, which made them a traditional way to create brilliant green fireworks.

The colour comes from the metal’s light emission, not from smoke. The article lists strontium for red, sodium for yellow, copper for blue and barium for green. This explains why removing barium changes the available chemistry for green effects. The green colour was linked directly to the compound used in the formulation.

Barium compounds are toxic, so the Supreme Court has banned them from crackers. The old form of brilliant barium green is therefore off the shelf, according to the article. Green-cracker development must use specially designed formulations that meet pollution requirements without relying on banned barium compounds.

The article places testing at the Emission Testing Facility of CSIR-NEERI, the national laboratory that developed India’s green crackers. Its scientists measure particulate matter, gases and noise, then compare a recipe with a conventional cracker of the same type. That testing supplies the evidence for whether the recipe meets the green standard.

Dr R J Krupadam leads NEERI’s firecrackers group and is quoted explaining the chamber, sensors and sound meter. The article also says the Supreme Court has banned barium compounds and has allowed only green crackers in Delhi-NCR during specified dates and hours. These are the organisations and authority explicitly named.

However, the article does not state which authority formally registers or approves a recipe for sale. It also does not describe a separate sales-licensing process. Based only on the text, NEERI performs the testing, while the Supreme Court sets restrictions, but the final registration authority is not identified.

A cracker’s chemical formulation stores energy. When it burns, that energy appears as heat, light, expanding gases and a sudden pressure change. The pressure change creates the sharp bang. The article describes the smoke as a mixture of solid particles and invisible gases, both produced during the burst.

Metal compounds explain the colours. Heated atoms absorb energy and release it as light of particular colours: strontium glows red, sodium yellow, copper blue and barium green. Burning sulphur in cracker powder forms sulphur dioxide. Other solid material becomes dust and soot, including PM10 and PM2.5, which scientists collect and measure.

The process is therefore not a single emission. It produces visible light, impulse noise, particles and gases at once. Green-cracker chemistry is designed to reduce smoke, dust and harmful gases compared with a conventional cracker. It does not remove the underlying burst, which is why green crackers can still produce substantial noise.