As to testing the exhaust of your classic car, I think your best option would be to take it to an MOT tester! If it doesn't have a catalytic converter, it will show carbon dioxide, water vapour, and rather more carbon monoxide than you might wish for, or which would be permitted on a modern car. You might not want to know that!
Yes, it's a boiler flue gas analyser to check the products of combustion emitting from the flue of a central heating boiler. As you might expect, time moves on and nowadays they are generally hand-held instruments about the size of a multi-meter, and often will print out the results of tests, as well as storing the test results. Typically they test boilers fuelled by Natural gas (methane), Light oil (28/35 sec), Propane, Butane, LPG & Wood pellets.
They carry out a wide range of tests:
Carbon dioxide (CO2)
Carbon monoxide (CO) 0-2,000ppm
Flue and inlet temperature
Differential pressure (±80mbar)
Calculates:
Oxygen (O2)
CO/CO2 ratio
Poison index
Efficiency
Typical example by Kane:
http://www.jmwlimited.co.uk/Kane_455..._Analyser.html
I don't know if the following remarks and reminiscences are a bit too far off topic and irrelevant. I'll leave that to the mods' judgement - I'm happy for them to be deleted if need be as they add nothing to the info about the actual Mobrey tester - only why such testers are necessary:
The products of combustion from a gas boiler working properly are carbon dioxide and water vapour, with a small trace of carbon monoxide and oxygen. If there isn't sufficient oxygen entrained into the burner, incomplete combustion arises. Methane is CH4. The H4 needs 2O2 to become H2O and the 'C' needs O2 to become CO2, but if it can't get it, it becomes CO, which is of course highly dangerous. (Carbon monoxide is 200 times more attractive to the lungs than is oxygen and hence, it's quickly absorbed into the bloodstream).
It's been mandatory for all gas boilers to be room-sealed for many years. What was called 'balanced flue', which have a concentric flue in which air is drawn into the combustion chamber, and flue gasses are emitted. There are still millions around - only about 60% efficient at best, and with a wasteful permanent pilot too.
The main danger was from open-flued boilers which were often sited in kitchens, where ironing takes place, and pets such as dogs and cats are often present. The fibres of pets and from ironing get drawn into the burner which can make the boiler hazardous.
Gas burners work on the 'venturi principle' - the jet of gas going into the burner draws air into the throat of the burner which mixes together and burns on a mesh or perforated burner head. When boilers (or any appliance such as a cooker or fire) designed for use on coal gas are converted to natural gas, the volume of gas required is halved, so the jet of gas into the burner is much less, and hence, it's ability to entrain air into the burner is much reduced.
The flame speed of natural gas is far less than coal gas, so with insufficient oxygen into the burner, incomplete combustion occurs generating carbon monoxide and the flame can lift off the burner (rather like a cigarette lighter when turned up too high), causing soot to form on the heat exchanger. Not helped by animal fibres and dust from ironing being drawn into open-flued boilers, blocking the burner mesh or holes. If the carbon monoxide enters the room rather than going up the flue, it can soon be fatal.
Nowadays, all boilers must be room-sealed fan-assisted condensing boilers, both for efficiency, (90% + of the gas is turned into heat) and for safety. A condensing boiler has a secondary heat exchanger to extract the heat from the products of combustion ('fumes') so that the hot H2O vapour condenses to water and is drained away, leaving mostly CO2 into the atmosphere.
I spent my career in British Gas, some of which was in the labs during the natural gas conversion programme, designing and testing burners to convert obsolete appliances designed for coal gas to get them to work on natural gas. Open-flued boilers were a particular problem due to their domestic settings outlined above. We used to check the flue with 'Draeger tubes' - glass tubes which you snapped off the end, and with a hand-held squeeze pump suck air into the tube to check the level of CO and CO2. The boilers back then would never have passed current tests.
From the late 1970s to the late 80s I was BG service manager at Sheffield. I used to attend coroners' inquests to give evidence several times a years where fatalities - often multiple - arose due to poorly maintained appliances, mostly open-flued boilers or wall-mounted gas fires. (So often in fact that I used to receive a Christmas card from the Coroner's Officer).
I always wondered on those tragic occasions, why so little was fuss was made and so little done about it in terms of appliance design and mandatory tests, so it's reassuring to see how far things have progressed over the years to make appliances far safer and more efficient, and to introduce mandatory landlord checks on gas appliances. (It was a landlord jailed in Hull for manslaughter due to a fatality in a student flat which I believe finally caused such mandatory checks to be implemented).