What’s The Difference?
For personal users
Unlike the situation faced by a business or other organisation that is testing a potentially “uncooperative” subject, the owner of a Personal Breathalyzer is, by definition, interested in doing the best they can to ensure an accurate sample.
For this reason, while professional devices need to have sophisticated means to ensure that every sample is sufficient and consistent a personal detector can rely upon the user themselves to some extent to use the device in exactly the same way every time. To blow at the same pressure, to ensure deep lung air is blown through the detector and also to ensure that it is not used in circumstances that may damage or contaminate the sensor. For this reason Fuel Cells are exclusively used in Professional detectors, because while they are also more accurate (and expensive) they are also more tolerant to contaminants such as excess alcohol, spittle, smoke etc that may be blown through the device by someone deliberately trying to “fool” the detector.
The semi-conductor sensors on the other hand that are used in personal detectors, while not as robust and accurate as the fuel cells can nevertheless give very good comparative readings when someone is looking to see how long it takes them to get back to zero after a certain level of consumption.