Monday, October 30, 2006

Chennai car accident - CO poisoning

I heard about this freak accident in Chennai. I read the news in Hindu. FYI: Hindu has new service called epaper, that can be accessed from

This incident happened in Chennai on October 28th night. Three software engineers decided to head out in Hyundai Santro Car. They got stuck in G.N. Chetty road, T. Nagar due to heavy rain. They decided to wait for sometime, parked the car, rolled up all the windows, switched on air conditioner and waited...Sometime later, all of them died due to carbon monoxide poisoning.

Here's a possible reconstruction of the tragedy according to The Hindu.

The air-conditioner is running and set on 'recirculate' - a mode people normally use to prevent the smellier components of urban air pollution from getting into the car. The engine is running to keep the air con functioning.

In the meantime, water is rising below and around the car, and this means the hot exhaust gas, which normally has a larger volume of air to disperse into, is suddenly crowded up against the undersides of the car's floorboards. The situation might be more adverse if the car's exhaust system has a leak somewhere and all emissions are not properly exiting at the tailpipe as they are meant to.

The gases might therefore be building up more heavily than normal under the car and inside the engine bay. And invariably, this gas will get into the car through the tiny access holes present in these regions - the little holes on the floorboard that drain water from inside a car, the innumerable gaps and holes that route wiring, cabling and mechanical controls like the steering column through the engine bulkhead - the wall that separates the engine bay from the passenger cabin. In the meantime, the air-con is steadily recirculating the deadly gases through the cabin of the car - and a silent and deadly killer gas -carbon monoxide - goes to work, poisoning the unwary occupants.

How does CO kill?

Carbon monoxide, or CO, is one of the gases emitted by your car's exhaust system. It is completely imperceptible to the human senses, being odourless, colourless, tasteless. And this poison is doubly deadly, as it gets absorbed into the bloodstream quickly - the haemoglobin in blood has a much greater affinity for this gas than oxygen, forming a strong bond that is devastating in nature - it starves organ tissues in the human body of vital oxygen. Symptoms of CO poisoning are things you'd shake off as the result of a stressful, long day at work - headache, dizziness, nausea and fatigue. And then you might decide to sleep it off for a while...

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