Why should you care?

For many people in California, smog checks are a mandatory thing every other year. This is to reduce the hydrocarbons, carbon dioxide, and nitrogen oxides that are released by the engine. Nitrogen oxides and hydrocarbons, also known as volatile organic compounds (VOCs), are especially important to keep track of as they can combine to form ozone. The health impacts of breathing in ozone can be hazardous; at best airways will be irritated, at worse asthma can be developed and lung tissue can be damaged. Fortunately, ozone levels can be reduced with the use of a catalytic converter. Most cars have them and they reduce the amount of nitrogen oxides (NOx) that are released.

How it can be done

With a pump and a filter, particulate matter can be measured by finding the difference in the mass of the filter paper from before and after air from the tailpipe is pumped through it. The filters gathered a range of amounts of particulate matter, from 0.00015 to 0.0283 g/L of air flowing through the filter. The average amount of particulate matter we found was 0.0055 g/L.

A NO₂ absorbing agent (containing glacial acetic acid, sulfanilic acid, and N-(1-naphthyl) ethylenediamine dihydrochloride) was used to help measure the nitrogen oxides that are released by a car. When it comes into contact with NO₂, it turns into a pink-magenta color after a few minutes. The plunger of a syringe containing 10mL of the absorbing solution was drawn back so that 50mL of air from the tailpipe was collected. The solutions can be compared to a calibration curve made from standards of NO₂ and the absorbing solution at different concentrations in order to find the concentrations of the car samples.

Our findings

On the cars that were tested, the general trend was that NO₂ concentrations were higher when the cars were first started, before their engines could warm up, which makes sense because it takes time for the catalytic converter to warmup. There didn’t seem to be a trend between the age of the car and its emission levels, as a 2017 Chevy Camaro released more NO₂ than a 2007 Jeep Cherokee. Other factors like the model of the car and the upkeep of it may also play a role.

Check-ups on cars should be done often even in areas that don’t make it a requirement. And if you don’t have access to a UV-spectrometer or NO₂ absorbing solution, a trip to your local mechanic should suffice.