Best combustion analyzer

The Bacharach Fyrite Insight Plus is the analyzer I’d buy for gas water heater and boiler work, and I’ve used it. This is the standard kit, part 0024-8517, sold by SIM Supply when we checked.

It reads more of the job than any other pick at this level. Bacharach’s data sheet lists O2, flue CO from 0 to 4,000 ppm, stack temperature to 1,202°F and primary air temperature.

It also reads draft and differential pressure to ±40 inH2O. That range scored a 10, and it means the same tool can check vent draft and gas pressure.

The CO sensor has a built-in NOx filter. Bacharach’s B-Smart program ships pre-calibrated CO sensors to your door, so you swap one in the field without calibrating it there.

It runs on four AA batteries or an optional USB wall adapter. Bacharach rates it at 15 hours minimum on alkaline cells, which scored a 10. Spare AAs are in every truck.

Reports scored a 10 too. The data sheet says it works with Bacharach’s reporting app, where you build as-found and as-left reports with your logo and email them to the customer. It also has an IrDA port for Bacharach’s printer and stores 100 locations.

The screen is a 2.8 in color display with up to 3x zoom. Bacharach’s Tune-Rite feature analyzes the combustion readings and gives troubleshooting suggestions on the spot.

Know two limits. CO2 is calculated from the other readings, which Bacharach says plainly. And the warranty is 2 years including sensors, with 3 years on the long-life O2 sensor that this listing names. That scored an 8.

My call: if you test every gas heater you install, this is the one to own.

The Fieldpiece CAT45 is the one I’d pick to keep sensor costs down, and I’ve used it. This is the CAT45 analyzer, sold by Voomi Supply when we checked.

Its warranty is the reason. Fieldpiece covers the O2 and CO sensors for four years, the longest of these five, and that scored a 10. The device itself is covered for one year. Fieldpiece says its SensorVault design prolongs sensor life and that both sensors can be replaced in the field.

It reads flue CO from 0 to 4,000 ppm with a NOx filter, another 10. O2 runs 0 to 21%. CO2, excess air and efficiency are calculated, per the manual.

Draft is where it falls short. The probe reads draft from 0 to ±0.8 inWC, and the manual warns that 4.0 inWC will damage the pressure sensor. So it checks vent draft but isn’t a tool for gas pressure, which scored an 8.

Reports scored a 10. The CAT45 connects to Fieldpiece’s Job Link app with a stated 1,000 ft wireless range, Fieldpiece sells a wireless printer, model CATPR, and the manual says it stores about 1,000 jobs.

It also reads room CO from 0 to 200 ppm, so you can check the air by the appliance before the probe goes in the flue. Fieldpiece rates the CO sensor for an overload of 10,000 ppm, and the analyzer weighs 1,120 g.

The screen is a 5.5 in touchscreen, the biggest here. The battery is a built-in 6,400 mAh pack that charges by USB-C and can be used while charging.

Run time is its weak spot. The manual lists 7 hours typical with the pump running 80% of the time, the shortest of the five, a 7. Charge it every night.

My call: buy it if you’d rather plug in each night than pay for sensors later.

The testo 310 II is the compact one with the best phone app of the group, and I’ve used it. This is kit 0563 3104 01, sold and shipped by Amazon when we checked.

It reads a lot for its size. testo’s data sheet lists O2, flue CO from 0 to 4,000 ppm, flue and ambient temperature, ambient CO to 4,000 ppm, draft from −8 to +8 inH2O and pressure from −16 to +16 inH2O. That gave it a 10 on CO and a 10 on draft and pressure.

One note on CO: testo says its reading is without H2 compensation. CO2, efficiency and flue gas loss are calculated.

Reports scored a 10. The testo Smart App shows readings, documents the job and keeps customer data, and testo sells a Bluetooth printer, part 0554 0621. The analyzer itself saves reports to the app rather than in memory.

testo’s data sheet says the app can add readings at the same time, such as gas flow pressure and flow and return temperature. The analyzer is rated to work from 23 to 113°F.

Power is a 1,500 mAh rechargeable lithium battery that charges over USB-C. testo rates it at more than 8 hours with the pump on, which scored an 8.

Small touches help on a job. There’s a built-in condensate trap, magnets on the back to hang it on the burner, and the sensors zero in 30 seconds after you turn it on. It weighs about 660 g with the probe.

The kit comes with the 180 mm probe, a silicone hose for pressure, five particle filters, a case, a charger and a certificate of conformity.

It scored a 5 on warranty because the data sheet doesn’t state one. Ask the seller what coverage comes with it.

My call: it’s the easiest to carry, and it’s the one Amazon sells directly.

The Bacharach Fyrite InTech is the plain, long-running analyzer of the group, and I’ve used it. This is kit 0024-8523, without a printer, sold by Megamart USA when we checked.

It does the basic test well. Bacharach’s data sheet lists direct readings of O2, CO from 0 to 2,000 ppm, and stack, ambient and combustion air temperatures. Efficiency, CO2, excess air and air-free CO are calculated. The lower CO range scored an 8.

Battery life is the standout. Bacharach rates it at a minimum of 20 hours on four AA alkaline batteries, the longest of the five, a 10.

The CO sensor is a B-Smart pre-calibrated part you can replace in the field. A CO shut-off feature protects it from over-range gas. The warranty is 2 years on the instrument and both sensors, an 8.

It has limits. There’s no draft or pressure reading, which scored a 6, so you’d need a separate manometer to check draft. It stores up to 10 records, and a printer is an add-on, which scored a 7 for reports.

Air-free CO is calculated up to 9,999 ppm, for heater manuals that ask for an air-free number. Bacharach’s data sheet lists EN 50379 and EN 50270 approvals, and the printer it pairs with is Bacharach’s optional IrDA model.

It’s set up for six fuels: natural gas, oil #2, oil #6, kerosene, B5 and propane. Bacharach says it’s American-made, and the kit adds a rubber boot and a hard case.

One listing note. The Amazon listing says European calculations, but Bacharach’s ordering table lists 0024-8523 as the standard kit and the European models under other numbers.

My call: it’s enough for a plumber who tests a few heaters a month.

The UEi C161C is the odd one out in a useful way, and I’ve used it. This is the analyzer with its carrying case, sold by 17Photo when we checked.

It measures CO2 directly. UEi’s data sheet calls it a flue gas analyzer with direct CO2 measurement, and its manual says it uses UEi’s own sensor for CO2. O2 is calculated instead. Every other pick here does the reverse.

Flue CO reads from 0 to 2,000 ppm, with an optional H2-compensated range to 10,000 ppm. That scored an 8. The CO sensor is NOx filtered, and low flow detection shuts the pump off if flow drops.

It adds tests the others don’t list. UEi names a heat exchanger test, differential temperature, high altitude compensation and an automatic fresh air purge.

It has no draft or pressure reading, which scored a 6. UEi’s own manual lists draft among the checks for a water heater, so you’d need a separate gauge for that step.

UEi lists TUV approval to EN 50379 parts 1 to 3 and AHRI 1260, and says it’s made in the UK. It’s set up for eight fuels and weighs 1 lb 5.1 oz.

Power is three rechargeable AA cells with USB charging, rated at more than 8 hours with the pump on, an 8. It stores 30 readings and prints to UEi’s optional IR printer, an 8 for reports.

The warranty takes reading. The manual’s standard warranty is 1 year, a 7. UEi’s page offers up to 10 years if you pay for its Service+ recertification each year, listed at $89.06 a year for years one to four.

My call: pick it if direct CO2 matters to you, and plan on the yearly recert.