At 5 o'clock on an October morning, a scrawny man in his late 30s hops onto a bus. Behind him, a young woman carrying a tiffin box calls out to wait for her. She is just in time before the bus hurtles past tiny lanes with rain puddles left by the previous night's downpour — the air reeking of a sour odour of sulphur and sadness.

As the bus stops in front of a huge iron gate, its occupants gingerly walk inside the gate behind which tiny matchbox-like bunkers greet them. It is in these 10x10 sqft rooms that men and women work together — from dawn to dusk, in sickness and health, in life and death to produce an array of firecrackers that illuminate the Diwali skies across India.

Welcome to Sivakasi — the fireworks hub in Virudhunagar district, about 544km from Chennai. Also known for its matchbox and printing industries, the Tamil Nadu town caters to almost 90% of the country’s demand. The townscape is dotted with numerous fireworks factories — over 2,000, in addition to around 1,000 illegal units, employing an estimated four lakh people —  inside which women could be seen furiously rolling cardboard paper into cubes and tubes while men, coated in aluminium dust, fill those tubes with a mix of chemicals like potassium nitrate and sulphur. Yet almost no one wears gloves or masks. These chemicals often have dangerous effects on their health, resulting in grave respiratory and skin diseases.

“Since, the work involves a lot of combustible materials, right from papers to chemicals, most factories do not have windows for these rooms and electricity connection to avoid any fire accident,” says a worker from Thayalpatti, a village about 15 kilometres from Sivakasi town.