Both the Senco Model One, left, and CO ûExperts are low-level monitors. CO Experts ûhas the most sophisticated self-calibration ûbut it’s more expensive by half.

Aircraft heaters seem to either fry your feet with enough BTUs to melt your Nikes or they dispense desultory little puffs barely warm enough to keep your breath from completely frosting the inside of the windshield.

Then there’s the aroma, that unique vague smell of exhaust and warm oil that always carries with it the potential for pumping enough carbon monoxide into the cabin to gas a small herd of cattle. If you’re real lucky, the CO will remain at the whiff level, just enough to allow the passengers to drift off on a long flight but not enough to turn everyone’s skin that festive shade of cherry red. …