Over 25 hospitalised after ammonia gas leak in Chennai's Ennore: What you need to know

On Tuesday night in December, around 11.45 pm, a leak occurred at a fertiliser plant in Ennore near Periyakuppam, north Chennai.

The leak emitted an unpleasant odour, prompting hundreds of residents to take to the streets, complaining of difficulty in breathing, discomfort in their eyes, and face.

The situation turned severe, resulting in over 25 people being hospitalised.

What

• Late on Tuesday night, there was an ammonia gas leak from an underwater pipeline supplying an industrial unit near Periyakuppam in Ennore.

• The leak was identified in the sub-sea pipe owned by Coromandel International Limited.

• Residents near the manufacturing facility reported feeling unwell, experiencing discomfort, nausea, and faintness.

• More than 25 individuals were taken to nearby hospitals for medical attention, reported PTI.

In a statement issued on Wednesday, Coromandel International Limited's President mentioned an abnormality detected on December 26, 2023, at 11.30 pm in the ammonia unloading subsea pipeline near the shoreside outside the plant premises.

The company promptly activated its Standard Operating Procedure, isolating the ammonia system facility and restoring normalcy.

How the gas leak happened

Pressure drop during pre-cooling process 

• During late hours on December 26, 2023, while conducting the pre-cooling process, Coromandel noticed a pressure drop in the pipeline.

• Gas bubbles were observed coming out of the pipeline approximately 2 feet from the shore.

Odour detected by locals

• Residents in areas like Periyakuppam, Chinnakuppam, Netaji Nagar, and Burma Nagar noticed a pungent odour around 11 pm where the pipelines pass.
• Intense odour and eye irritation were experienced.

Evacuation and inspection

Families from the affected areas evacuated to safer locations like temples, community halls, and public schools around midnight.

Officials arrived at the site for assessment, monitoring, and inspection of ammonia levels in the air.

Exceeding limit

Over three hours after the leak, TNPCB's inspection at 3:30 am revealed the ammonia level in the air to be 3 ppm, equivalent to 2090 micrograms/m^3, surpassing the 400 micrograms/m^3 standard on a 24-hour average.

The ammonia level in the seawater sample at the point of pipeline leakage at 3:49 a.m. was found to be 49 mg/litre, exceeding the marine discharge standard of 5 mg/litre.

In Tiruvallur, Tamil Nadu, residents staged a protest following the discovery of an ammonia gas leak.

Ammonia handling and transportation process

• The Coromandel International Limited facility in Ennore regularly receives and unloads ammonia shipments sourced from Iran or Saudi Arabia, ranging from 3000 to 8000 tonnes every month.

• Ammonia arrives in liquid form at an extremely cold temperature of -33 degrees Celsius and is stored in a tank under the same conditions.

• Transportation is facilitated through an eight-inch flexible High-Density Polyethylene pipeline beneath the seabed.

Despite timely depressurization and evacuation efforts, TNPCB inspections revealed ammonia levels exceeding safety standards, causing concerns among residents and leading to protests.