A few years ago, new owners remodeled the house across the street from mine. The contractor drove a shiny diesel pick-up that he used as a mobile office — parking and sitting in it while he made phone calls or did paperwork. I work at home, so was frequently treated to the sound of the idling truck. One day when he’d been out front a good 45 minutes or more, I walked out my door and the smell of exhaust nearly bowled me over.

You’ve probably run into idling buses in national parks, bike trails and the school pick-up line.

Diesel engines have lower per-mile fuel consumption than conventional gas engines, so they generally emit less carbon dioxide while on the road. But according to Deanna Altenhoff, executive director of the Clean Air Force of Central Texas, diesel exhaust includes nitrogen oxides (NOx), a precursor to ground-level ozone, and particulate matter, tiny soot particles that can lodge in the lungs and that are a potential carcinogen.

“Of the 61.14 tons per day of NOx emitted from on-road vehicles in Central Texas,” Altenhoff said, “29.67 come from diesel vehicles.” Breathing even small amounts of diesel exhaust can inflame the lungs and trigger asthma attacks — especially in children and the elderly — and studies have linked exposure to diesel exhaust with cancer, heart attacks and premature death.

Limiting engine idling is a simple way to reduce potentially harmful emissions, and a state rule even limits diesel idling to less than five minutes. (Anyone can report violations by calling 512-343-SMOG within 30 days. Reporting is free, and you don’t have to give your name.)

It’s a good idea to limit idling of all vehicles, not just diesel ones, given that Houston is one of nine areas in Texas that do not meet clean air quality standards, and vehicle emissions are a contributing factor. Idling vehicles may be a small part of our air quality problems, but they’re one part that’s easy to solve.

Across the U.S., idling cars burn some 1.4 billion gallons of fuel; trucks burn another 1.5 billion gallons, emitting about 58 million tons of carbon dioxide. All while accomplishing nothing. When idle, you're also producing carbon monoxide — an invisible, odorless, poisonous gas. Driving, of course, produces carbon monoxide too, but when you’re not moving, you’re sitting in a cloud of it.

Turning off and re-starting your car uses less gas and produces less carbon monoxide than idling for a half a minute. That’s 30 seconds — a pretty short amount of time. Limiting engine idling is pretty easy, too. Park and go inside rather than using a business's drive-through. You’ll probably save time as well; I frequently park, go in and get my coffee or make a bank deposit, and return to my car before I would have made it to the window.

If you must use the drive-through — say, you have a sleeping baby with you — turn off the car while you wait.

Idling also increases wear and tear on your engine. According to the EPA, idling causes twice the wear on internal parts as driving at regular speeds. An idling engine is not operating at optimum temperature, which causes incomplete fuel combustion and leaves residue on spark plugs and cylinders. Excessive idling also causes water to condense in the exhaust, which increases corrosion.

New diesel engines stay warm for several hours after they have been running, Altenhoff says, retaining more than enough heat to avoid starting difficulties. In very cold weather, it may be necessary to warm up a diesel engine for three to five minutes, but not any longer than that.

So, all you idlers out there: Turn off your engine. You’ll save gas and money — and we’ll all breathe cleaner air.