If you’d rather not burn a candle or incense in your kitchen, you can buy a smoke stick, which is what French uses in his own testing.
As far as testing the levels of carbon dioxide and carbon monoxide in your kitchen, French suggests leaving that to the pros, because most affordable, commercially available units are either prone to false alarms or require constant calibration. That said, you should always have a functioning carbon monoxide detector on every floor (just don’t keep it in the kitchen, again, because of false alarms).
For a more complete picture of what you’re breathing in at home, consider an indoor air quality assessment. You can find a professional assessor on the IAQA’s website, though French (a pro assessor himself) says that if you’re mostly concerned about air pollution from cooking, there’s plenty of data online that can tell you what you’re releasing when you prepare certain foods on the stove and in the oven. For example, a 2001 study (PDF) found that broiling fish “produced very high levels of particles in the kitchen and other rooms of the house” and that the self-cleaning function on any gas or electric range might just be opening a portal to hell.
What to do if you don’t have functional kitchen exhaust
If it turns out you don’t have a functional oven hood—or if you don’t have a hood at all—there’s no need to panic. And no, you don’t have to renovate your kitchen, either. There are a few far-less-expensive steps you can take right now to mitigate the indoor air pollution caused by cooking.
1. Install a ductless range hood
Though usually not as effective as a hood that vents to the outside, a ductless hood can still capture oil vapors and other contaminants through a series of filters before recirculating the cleaner air back into your kitchen, similar to an air purifier. Often, these hoods are called convertible, meaning that in addition to the ductless configuration, they can be connected to an existing duct system.
No room for a full-size hood? You can still install a compact version under upper cabinets, or swap your mounted microwave for one with a decent built-in exhaust system.
If you go for a ductless hood, be sure to clean and/or replace the filters regularly. When I finished chatting with French, I immediately inspected my own and was both pleasantly surprised and completely disgusted by how much gunk it had captured since I last cleaned it.
2. Get an air purifier for the kitchen
An easier solution is to get an air purifier for the kitchen. In addition to making sure the unit you pick is powerful enough to match the size of your space, look for something with both HEPA and VOC (volatile organic compound) filtration. The HEPA filter will catch particles and oil vapors while a chemical/VOC filter will capture strong smells and hazardous fumes.
Keep in mind, however, that a dedicated kitchen air purifier is bound to trap grease, grime, and dust in a way that a unit in a living room or bedroom will not, which is why manufacturers generally recommend against placing an air purifier directly next to or above a cooktop. But the closer it is to the source of the pollution, the more effective it will be, says French. Of course, in order for it to remain effective, it’s imperative to replace the filters and clean the machine regularly—much more frequently than the manual or indicator lights suggest, according to French.