Foobot Indoor Air Quality (IAQ) monitors are our personal favorite. They measure and record readings for temperature, humidity, dust (PM2.5) and chemical pollutants (VOCs). These are very useful for understanding if there is a problem to solve in your home, and also if it gets solved. See our complete review of 7 IAQ monitors.

Flir One infrared camera for iPhone. Click through for Android version. I use a first generation one and love it. Does 80% of what a $3000 IR camera does for less than 10% the price. Not super useful unless you have a blower door or a powerful range hood to depressurize your house and find leaks. The price fluctuates, $249 or less is good.

Very inexpensive temperature and humidity gauge. Buy a few of these and put them around the house. Start noting the swings. They tell you the high and low in the last 24 hours, and they’re very inexpensive. Watch for humidity over 60%, it should never get above that. They’re not crazy accurate, +/- 5% or so. If it’s in the budget, get a datalogger like a Foobot.

Hobo temperature and humidity datalogger. A lovely little tool that you can put in a hard to get to place like inside an attic or ductwork. Use where wifi and/or power aren’t available. Batteries last about 6 months. Use Bluetooth on your phone to download data. 

Temperature and humidity detector with 3 remote sensors. If you want to keep costs down while diagnosing your home, start here. Put one remote sensor outside and the others on different floors or even in the attic. Look for differences and patterns. Check Amazon for other similar options.

A Wizard Stick is a simple smoker. This is what I use for testing for air leaks (besides my hand and an infrared camera.) If you have a powerful range hood, it could act like a blower door and you can use this to find leaks.

NetAtMo is my second favorite IAQ monitor. This weather station also monitors indoor carbon dioxide (CO2). It has an outdoor module as well for temp and humidity. Very nice app and webapp. Somewhat finicky sensors, CO2 can go out of whack, it doesn’t like dusty environments.

Awair IAQ Monitor. The best looking IAQ monitor, but mediocre calibration of humidity and VOCs. That plus only 1 week of data in the app take it out of the running for me. See our complete review of 7 IAQ monitors.

Infrared thermometer. If a Flir One doesn’t fit your budget, consider one of these. It only takes one point of temperature vs. thousands or millions for IR cameras, but it’s a start. Good for reading surface temps and feverish kids, too. Big boxes carry similar items.

Calibration kit for humidity monitors. The kit is at 32% relative humidity, put your monitor inside. If it’s 5% high, subtract 5% from the readings, and so forth. If you’re a super geek, spend the $8.

Corentium radon detector. Long term average as well as short term 1 day and 7 day averages. Battery powered, easily moveable. You can find out if there are hot spots in your home, and have an idea if your upgrades worked.

Dylos 1100 Pro Particle Counter. This is the only one that measures below 2.5 microns. The “small” range is only available on the pro model. It is 0.5-2.5 microns. No wifi connection, only downloadable onto a PC. A battery powered version is also available. See my complete review on IAQ monitors.