KUALA LUMPUR: People are strongly advised against sleeping in vehicles with the engine idling, even with the windows slightly wound down. Experts say this is important if a car is five years or older as there is a risk of carbon monoxide (CO) poisoning.
Dr G. Jayakumar, a professor of Community and Occupational Medicine at the Faculty of Medicine in Melaka Manipal Medical College, said it was a common misconception that there was sufficient ventilation in a vehicle for one to rest or sleep with the engine and air-conditioning (AC) running.
He said the occupants of the car will not be shielded from the harmful effects of CO poisoning as the gas will enter the vehicle and accumulate.
He said that when this occurs, drivers and passengers are at risk of CO exposure which leads to lower oxygen and body fluid levels.
This CO exposure causes serious complications, including brain damage and heart problems or even sudden death in severe cases.
"It is not safe to sleep in a car with the engine running and windows closed except in an emergency.
"It is advisable to park at a shaded area if travelling during the day as temperature build-up in the car can be dangerous," he told the New Straits Times.
Jayakumar said the subtle warning signs to CO poisoning are a dull headache, weakness, dizziness, nausea or vomiting; while the more serious signs are shortness of breath, confusion and blurred vision.
If people experienced such symptoms after sleeping in a vehicle with the engine running, he advised them to immediately come out to an open space.
His comments followed the tragic incident on Wednesday where three college students, who fell asleep in their car with the engine running, died from CO poisoning. A fourth person is in critical condition.
Universiti Kebangsaan Malaysia Chemical Sciences Department senior lecturer Dr Darfizzi Derawi said CO is a poisonous gas that has no smell or taste and cannot be seen by the naked eye.
"Breathing it is harmful and may be fatal if exposure exceeds the Permissible Exposure Limit, which is only 50 ppm (parts per million) within eight hours of exposure.
"When the CO is breathed in, it enters the bloodstream and mixes with haemoglobin, the red blood cells that carries oxygen to the entire body, to form carboxyhaemoglobin.
"When this happens, the blood is no longer able to carry oxygen, and this lack of oxygen causes the body's cells and tissue to fail and die."
Darfizzi said the vehicle-engine combustion process produces CO under incomplete burning conditions.
He said all brand new vehicles are equipped with a catalytic converter (CC), which turns any toxic gases into less harmful gas. However, this system depends on many other factors.
"If the CC is not well-functioning, the conversion may not fully happen, and CO may not convert to CO2.
"Driving a vehicle with the unfixed problems produces CO, which will disperse into the surrounding areas. But when the vehicle is idle for a long time, CO may re-enter the vehicle, and it is inhaled by the driver or passenger."
Darfizzi advised vehicle owners, especially those with cars over five years, to conduct regular checks at reputable service centres based on the vehicle's service schedule.
He said owners must repair the exhaust system or replace the CC, if need be.
"Any leaks in the exhaust system can result in accidental CO poisoning.
"If these have been checked, resting and sleeping for a short while in the vehicle is not a problem. Opening windows is not an absolute solution for this matter."
Malaysian Public Health Physicians' Association president Datuk Dr Zainal Ariffin Omar said remaining in the vehicle for about an hour or two with the AC and engine running and window slightly open was fine, provided the exhaust is in good condition.
"Avoid sleeping in cars if possible. Keep the windows and air vents open and set an alarm to wake up.
"CO poisoning may lead to loss of consciousness, brain damage, heart problems, coma and death."