A $15 dollar investment could save your life. Consider installing a carbon monoxide (CO2) detector in your cab. Every year, dozens of truckers or their riders, become sick or even die from inhaling CO2. Whether it is from as faulty exhaust, an improperly vented propane heater, or parking next to someone at a truck stop while their main engine, diesel APU or reefer is running, CO2 poisoning happens to truck drivers.
You might consider this $15 battery operated one from Target.