Every year, we hear unfortunate stories about kids being left in cars. Hot cars are one of the most dangerous places to leave a human being, cellphone or pet. However, could that same car heat that make a car so dangerous be useful in the fight against coronavirus? Here’s an explanation.
A recent study published in the New England Journal of Medicine confirmed that coronavirus can linger on different types of surfaces for significant periods of time. For example, the study found the following “linger times:”
- cardboard shipping boxes – 24 hours
- plastics – up to three days
- stainless steel – up to three days.
If you are like my family, you probably have been ordering many things from online distributors that arrive in boxes or plastic containers. My mitigation strategy has been to spray them with disinfectant or leave them sitting around for some period of time. However, one of my colleagues at the University of Georgia says that many of the media stories about virus lingering times neglected to mention that the studies took place at room temperature (roughly 72 degrees F).
In a news release from the University of Georgia, Professor Travis Glenn interpreted the study for the public. Glenn, who was not directly involved in the study, said “Coronavirus lives a few days on many surfaces at room temperature, but it dies far faster at higher temperatures.” The aforementioned study noted that SARS-CoV-2 (the novel coronavirus) was similar to SARS-CoV-1 and that their responses to heat may also be similar. Glenn points out in the press release that “If you heat a material up to 130 degrees F, which is the high setting on a dryer or a very low oven setting, you only need about 20 minutes to kill greater than 99.99% of the virus.” At 15o degrees F or higher, it only takes about five minutes to kill the same percentage of virus. However, it may not be practical to throw your mask or package in the oven. The clothes dryer is a good alternative for the masks, but what about those packages?
Here is where your car and something called vehicle heating dynamics comes into play. Jan Null is a meteorologist with Golden Gate Weather Services who has studied child deaths in hot cars for many years. His website is one of the most thorough places to go for information about the topic. Null suggested to me that cars might be useful agents for killing the virus on packages. Scientists like Null and my colleague Andy Grundstein at the University of Georgia have warned us for years to be diligent about not leaving kids, pets, or electronics locked in cars. Here’s why.
According to Null’s website, “The atmosphere and the windows of a car are relatively “transparent” to the sun’s shortwave radiation (yellow in figure above) and are warmed little.” As you see in the graphic (or from your own personal experience), it is brutally hot inside a car left in the sun. Dark materials (dashboards, seats, and other objects) heat up significantly and then heat the air through the processes of convection and conduction. The objects also emit infrared (heat) energy. However, this automotive “greenhouse” effect could be useful in killing coronavirus according to Null.
Null and colleagues published a study in the journal Pediatrics in which they found that it doesn’t take very long for temperature to rise in a car. Here were some of the elapsed times and temperature changes in their study:
Average elapsed time and temperature rise
- 10 minutes ~ 19 deg F
- 20 minutes ~ 29 deg F
- 30 minutes ~ 34 deg F
- 60 minutes ~ 43 deg F
- 1 to 2 hours ~ 45-50 deg F
- 2 to 4 hours ~ 50-55 deg F
A more recent study by Grundstein also affirmed and extended these number. Null says that one place to get the heat required to kill the virus on a package might be the mask. However, it is important that only inanimate objects or products not sensitive to heat be considered for this practice. Dr. Calvin Mackie is a renowned engineer and STEM ambassador. The founder of STEMNola told me, “I keep my mask on the dashboard of my car for this reason.”