BASIC Ozone O3 Detector & Meter by Forensics | Handheld | Li-ion battery recharge via Micro-USB | 0 - 5ppm range |

My reading was over 1ppm which seams much higher than Osha required limits for residential property. I called the company regarding how to do thecalibration and they said no need to. Hope they can respond to my issue

Works good shows 0 ozone another review stated his was not working because when he held it over a fan it showed a ozone reading when he breeds on it he said it showed a ozone reading so he said it was defective. Well it turns out mine did the same thing except I contacted customer support it turns out the sensor has to be heated to get an accurate reading they told me not the hold it over moving air because it cools off the sensor and give you a false reading so I did what they said I just moved it around the room and I can say I got zero ozone so this is a good product just don't put it in front of moving air and it will be accurate

Although it is hard with this type of a device to find a reference value, comparing to other devices I had, it did not produce the same level sensitivity I had with other units.

Probably the first thing to know is that the Forensics Detectors company has removed this item from their web site. It appears that they bought this cheap product in China and decided to slap their label on it (crookedly I might add) and sell it on Amazon. We tested it several times. Calibrated it more than once. Got high false readings (2 to 3 ppm!) in our office, higher readings in fresh air outside and then confirmed it's worthless sensor by placing it in a small test room where Ozone would be generated. The reading was ZERO ppm throughout this test and ended at ZERO ppm. The air was fresh at the test beginning and, by the end of the test, the air was unbreathable and dangerous. This "detector", which was constantly monitored, showed ZERO ppm the whole time. Junk! If we could give this product ZERO stars, that would be more fitting and appropriate.

Got the job done. Easy to use

It appears to measure ozone. Key word in the description is QUALITATIVE. Not sure what the factory calibration in California thing is all about, beyond them likely putting stickers with their name on it over the Chinese manufacturers name from alibaba, since you regularly have to go outside to clean air and hold the down button to reset it to zero. The up button appears to be a max hold, and the select button does nothing as far as I can tell.I have no sense of accuracy. Basically it's just a scale from 0 to 5 which I hope has some relevance to PPM and compared to when you referenced it. The readout is very sensitive to the charge state of the battery, so over time the reading will drop as the battery goes down, and if you charge it while using it it will jump up about 2PPM. Hence the need for regular recalibration.The sensor is very slow to respond. It takes at least 60 seconds for the reading to stabilize in the ozonated environment and about 10 minutes to drop back down again once removed from it. Also, the unit needs to be on in order to go back to zero. Just turning it off and waiting an hour will pick up with an elevated reading right where you left off.Pretty disappointed. The listing should have been more clear by all rights. But it will tell me if somewhere still has ozone happening in it which was really what I needed it to do. Speaks to the build quality though when they can't be bothered to put a voltage regulator between the battery and the sensor.

Very responsive.

It looked like it worked. However, wave in air--5ppm O3, blow on it--3ppm (I don't think I have ozone breath). Place on a fan--3ppm. Place in O3 chamber, 0ppm. I was rather concerned that moving air caused reading problems. In fact one of the uses I was after was measuring O3 for some fans with HEPA filters, to see if the electrical switches and wires inadvertently put O3 into the the filtered moving air. Also wanted to check AC unit for O3. Sent unit back. For a few $ more, I purchased a different unit from a different company without all of these issues, and measured O3 properly in an O3 chamber -- and it came in calibrated so I can cal other sensors I have.