My wife thought she occasionally smelled gas in one of the drawers in the kitchen. She even said, offhand, "Do you have a gas leak detector?" I said, "No." So she said, "You ought to get one." That was enough motivation for me. I went to Amazon, compared features and prices, and chose the Yeezou 201 Combustible Gas Detector.
When operating the Yeezou 201 features six LEDs that light up from 1 to all 6 depending on the concentration of the gas it discovers. There is a calibration knob, allowing the user to set a zero state. Just take the unit into fresh air, turn it on, wait about 10 seconds for warm up, and then rotate the calibration knob until the unit is just on the edge of alarming. Then place the tip of the gooseneck near joints and connections to see if there is a leak.
While sampling the air, the Yeezou 201 clicks at a low rate, just a few times a second. If it detects a leak, the clicking increases, the LED lights come on 1 to all 6 as I mentioned, and an audible alarm sounds.
I took the 201 unit and put the sensor under the cooktop, and got a one-light low alarm on two connections. So those need attention. Curious, I went outside to check a gas stub in back of the house. It was okay. Then I went to the gas meter at the service entrance and checked each joint. At the shutoff valve, the unit lit up a 6 alarm leak. I called the gas company and they sent out a representative who used the bubble check method to check the leak. He said it was a very low leak, enough to form bubbles, but not enough to break them. He replaced the leaky shutoff valve. I tested all the joints he had unscrewed and the Yeezou 201 found no new leaks.
Bottom Line: This is an excellent unit for detecting even very small gas leaks. For the price, every homeowner should have and use one. In addition to natural gas, the Yeezou 201 also detects other kinds of combustible vapors, such as propane, methane, gasoline vapor, butane, and more.