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Study finds ‘heat wave-like’ conditions in cars

Jacob Koshy

They may lead to ailments such as heat stress, heat strokes and fluctuation in blood pressure

The ambient temperature inside cars could shoot up to as much as 65°C and induce conditions akin to a heat stroke, says a study that measured temperature and relative humidity levels.

The objective of the study, led by researchers at the Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, was to assess “thermal comfort” (the degree of warmth that people deem as comfortable) in cars.

The study also evaluated people’s experience of thermal comfort in sedans, sports utility vehicles and hatchbacks, in Chandigarh.

“The predicted mean vote (PMV) was observed to be worst for Sedan for both front...the Percentage of Persons Dissatisfied (PPD) was observed to be 100% in all cases, showing dissatisfaction for all car models. The concentration of carbon dioxide and carbon monoxide ranged between 113-1127 ppm and 0–3.9 ppm, respectively, for the front of the car,” the authors Ravindra Khaiwal, Neha Agrawal and Suman Mor, note in their paper. The PMV and the PPD are metrics to measure thermal comfort.

“Understanding how thermal comfort varies during extremely hot and cold conditions in the micro-environment of a car could help auto industries improve thermal comfort and minimise the associated health risks,” Mr. Khaiwal told The Hindu. “This could mean designing new materials that absorb heat better, or improving the air flow system in vehicles.”

The measurements showed that the front of the car showed a higher maximum temperature than the back, while relative humidity was observed to be lower in the front than the back for all models. The temperature recorded in Sedan was higher than in SUV and in Hatchback. The higher temperature was due to ambient conditions on different days and also due to the colour of the car, the researchers found.

The higher temperature in Sedan may also be due to its black colour, which is a good absorber of heat while SUV and Hatchback were white, which has higher reflectance,” the study notes.

Mr. Khaiwal said conditions akin to a heat wave could manifest and — given changes in climate and higher average temperatures — would lead to several more ailments such as heat stress, heat strokes and fluctuation in blood pressure.

Understanding heat waves in micro-environments is also important given warming trends.

Last year was the seventh warmest since record-keeping commenced in 1901. The annual mean surface air temperature, averaged over the country, was +0.36°C above average. The average is defined as the mean temperature from 1980-2010.

The highest warming observed over India was during 2016 or 0.71°C above the mean. 2018, which was the sixth warmest, was 0.41°C, and 2017 was 0.55°C warmer, than the average.

According to the World Meteorological Organisation, the rise in global mean surface temperature during 2019 (January to October) was +1.10°C.

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