Combustion Analyzer

Combustion Analyzers and Combustion Analysis

Different Combustion Markets and Their Requirements

Although combustion is driven by the same underlying chemistry and physics in a residential furnace or industrial boiler, the operational, environmental, and regulatory requirements of combustion equipment and processes can differ greatly. This in turn creates different requirements for combustion analysis equipment across the residential, commercial, and industrial markets.

Residential

The residential market largely consists of home furnaces and hot water heaters, usually fueled by natural gas, propane, or oil. Since both these combustion appliances share the same physical space and air as people, safe operation is the primary and overriding goal. This is why carbon monoxide (CO) measurement is at the heart of residential combustion analysis and the baseline feature of every combustion analyzer intended for the residential market. Ambient air CO minimization is the top priority residential combustion appliance servicing. In fact, some equipment manufacturers offer standalone CO detectors in their residential portfolio.

One of the key ways to minimize CO levels in the ambient air of the home is to ensure adequate draft of the flue gases up the stack and into the outside air. Insufficient draft can cause flue gases—including CO—to spill out of the appliance and into the air surrounding it, causing CO levels to reach dangerous levels. This is why flue gas draft and pressure measurement is also a common feature found in residential combustion analyzers. Exhaust gas temperature of course is what ultimately generates the draft in appliances which utilize natural draft, but the direct measurement of the flue gas temperature is mainly used for achieving the secondary goal of residential combustion analysis: maximizing combustion efficiency.

Measuring and minimizing CO levels is just as critical to maximizing combustion efficiency as it is to maintaining safe operation. When carbon is fully oxidized, it forms carbon dioxide (CO₂). Thus the presence and level of CO indicates incomplete combustion, which is often caused by an inadequate amount of air.

Now back to the other key parameter for ensuring efficient combustion: the temperature of the flue gases. Many residential combustion analyzers take the exhaust gas temperature, specific fuel used, ambient air temperature, oxygen (O₂) level in the flue gas, and type of furnace (i.e. non-condensing vs. condensing) as inputs into a pre-programmed formula which models the combustion efficiency of the appliance. By calculating the combustion efficiency and displaying to the HVAC technician, that tech can confirm that the appliance is operating efficiently or adjust it as necessary.

Just as flue gas CO, O₂, draft, and temperature measurement are the standard features of residential combustion analyzers, they form the foundation of combustion analysis for the commercial and industrial markets.

Commercial

The furnaces and boilers used in the commercial market are bigger than residential furnaces and hot water heaters. They also consume more fuel and air, and tend to burn at higher temperatures compared to the residential appliances. In the commercial combustion analysis market, determining levels of other combustion byproducts in the flue gas such as sulfur dioxide (SO₂) and nitrogen oxide (NO) are additional requirements since regulatory restrictions on those pollutants are in effect on commercial combustion equipment. Commercial combustion analyzers therefore feature more standard gas sensors than residential analyzers.

Also, the concentrations of CO in the flue gases are also higher in the commercial market. Whereas many residential-oriented combustion analyzers measure CO levels only up to 4000 ppm, commercial analyzers have sensors which can report concentrations up to about 8000 ppm. Another change seen in the CO sensors for this market is the inclusion of a “NO_x” filter which blocks nitrogen oxide (NO) and nitrogen dioxide (NO₂) from skewing the CO sensor’s readings too high. The amount of nitrogen oxides increases as the combustion temperature does, and commercial combustion equipment tends to run hotter than residential appliances do. This is one reason why regulatory NO_x limits are commonly in place for the commercial combustion market and not the residential segment.

Since NO and NO₂ emissions reporting requirements vary from one jurisdiction to another, not all commercial HVAC techs will need to measure both or even either. This is one reason why customization in the form of optional gas sensor configurations is a common feature for commercial analyzers. When ordering, technicians can order which gas sensors and how many they want. In the field, techs can swap out the gas sensors on many of analyzers in this market, making them more efficient and flexible on the job, as the fuel composition, size, and combustion equipment type can differ greatly from one job site to the next.

Industrial

The trend of increasing combustion temperatures and gas concentrations continues on into the industrial combustion analysis market. CO measurement limits of 10,000 ppm and above are standard.

At this level, analyzers can have up to six sensors, with options to cover every substance which needs to be measured for combustion: O₂, CO, NO, NO₂, SO₂, and unburnt combustibles (usually abbreviated C_xH_y). Some manufacturers even include hydrogen sulfide (H₂S) as an option as well. Like their commercial counterparts, the gas sensors in these analyzers are field-swappable too.

Industrial combustion analyzers are sometimes bought by commercial HVAC techs who need O₂, CO, NO, NO₂, and SO₂ sensors installed at the same time, since commercial analyzers are commonly limited to just four sensor slots.

An Interesting Industry

Just as with any other high-level summary, the above breakdown comes with several caveats. For starters, the commercial segment is frequently further broken down by analyzer manufactures into “light commercial” and “heavy commercial”, with the latter overlapping with the residential end of the market. Overlaps also occur between the industrial and commercial markets.

In addition, the number and types of sensors associated with each market isn’t a universal rule. TPI (Test Products International) includes 10,000 ppm CO sensors in all their analyzers, even the residential ones. Some manufactures use different sensors for “high” and “low” CO concentrations, while others dilute the sampled gas and then multiply the sensor reading by the dilution factor to compensate.

Fundamentally, the different types of combustion equipment, fuels, and regulatory requirements dictate which class of combustion analyzer is best for each technician at each point in time. The traditional three-way breakdown of the analyzer market serves as a reliable initial guidepost in that process.

Popular Residential Combustion Analyzers

HVAC technicians looking to purchase a combustion analyzer for servicing residential furnaces would do well to start their search with the analyzers most commonly bought by their fellow techs. According to our data, the most popular residential combustion analyzers include two from Bacharach, two also from Testo, and one each from E Instruments and UEi.

Let’s start with two favorites from Bacharach: the 0024-8512 Fyrite InTech kit and the 0024-8518 Fyrite Insight Plus kit.

Bacharach Fyrite InTech Combustion Analyzer Reporting Kit

The Bacharach Fyrite InTech Combustion Analyzer Reporting Kit (P/N 0024-8512) kit is a very complete package built around the Fyrite InTech analyzer, which is Bacharach’s product aimed solely at the residential segment of the combustion market. The Fyrite InTech measures O2 and CO (up to a limit of 2,000 ppm), ambient temperature, and flue gas temperature. Like almost all other analyzers, the CO2 percentage is calculated. The Fyrite Intech has internal memory space for 10 tests.

It should be noted that the Fyrite Intech is not capable of measuring flue draft or pressure. Thus, technicians who will need to verify and measure flue draft will have to consider other analyzers—such as Bacharach’s own Fyrite Insight Plus (see below).

The 24-8512 kit also includes a rubber boot for the analyzer, a hard shell carrying case for durable protection, three spare particle filters, a printer, and measurement reporting software for transferring saved combustion tests to a PC.

The relatively low limit of the CO sensor restrict the Fyrite InTech and the 0024-8512 kit for residential use only. As we’ll see below starting with the Bacharach Fyrite Insight Plus (24-8518 and 24-8517), many analyzers cover both residential and light commercial combustion analysis needs. With greater capabilities, of course come higher price tags, which is why the 0024-8512 Fyrite InTech kit is an affordable favorite among HVAC technicians.

Bacharach Fyrite Insight Plus Combustion Analyzer Reporting Kit LL

As mentioned earlier, the Fyrite Insight Plus is a definite step above the Fyrite InTech—it’s built to handle both residential and light commercial combustion analysis.

Some of that upgrade comes down to increased specs:

Although the bulk of the Insight Plus’ advantages over the InTech is due to added features:

The Bacharach Fyrite Insight Plus Combustion Analyzer Reporting Kit LL (P/N 0024-8518) is the Insight Plus counterpart to the 0024-8512 kit, and contains all the same additional items as that kit does.

Testo 310 (P/N: 0563 3110 and 0563 3100)

Testo is another well-known brand in the combustion analyzer industry, and we see that reflected in the sales of both their 310 and 320 analyzers, along with the kits based on them.

The Testo 310 combustion analyzer, like the Bacharach Fyrite InTech, is aimed squarely at the residential combustion market. Not surprisingly, they share a few specs and features in common:

The Testo 310, however, differs from its Bacharach rival in several ways:

Two other features of the 310 worth mentioning are the automatic pump shutoff and fresh air purge when the analyzer detects a CO concentration above the range of the sensor. These features help protect the CO sensor, extending its working life.

Techs would have to buy up to the Bacharach Insight Plus in order to enjoy some of the features already included in the Testo 310. The Fyrite InTech does, however beat the Testo 310 in other areas (i.e. higher flue gas temp limit, one more pre-programmed fuel). Each HVAC technician will have the to carefully consider which residential analyzer best fits their work, needs, and budget. This same advice is true for every analyzer we discuss here.

That said, technicians who choose the Testo 310 will be pleased with the Testo 310 Combustion Analyzer for Residential Applications kit (P/N 0563 3100 01) which includes the analyzer, rechargeable battery, probe with connecting hose, hard plastic carrying case, silicone tubing for pressure measurements, five particle filters, an AC power supply with USB connector for recharging the analyzer, five pressure plugs, and a calibration certificate.

For a 310 kit which includes a printer, consider purchasing the Testo 310 Kit Combustion Analyzer Portable with Printer (P/N 0563 3110 01) kit. In addition to everything listed above, this kit contains an IR printer and 2 rolls of paper for it.

Testo 320 and Testo 320 Kit with printer (P/N: 0563 3220 70 and 0563 3220 71)

Testo’s 320 combustion analyzer is the next step up from the 310, and is designed for the residential and light commercial segments of the combustion market. As such, the 320 is Testo’s counter to Bacharach’s Fyrite Insight Plus.

Compared to the 310, the 320 adds a color screen, a higher flue gas maximum measurement temperature (2192°F), and a wider measurement range for draft (-4 to 16 inches H2O) and pressure (0 to 120 inches H2O) readings. The 320, however, shares the same CO maximum limit as the 310 (4,000 ppm).

The Testo 320 is compatible with plenty of optional probes for other measurements such as fuel gas leakage (up to 10,000 ppm of CH4 or C3H8), ambient CO2 measurement, high resolution pressure measurement, ambient air CO levels, draft, pressure, and differential temperature.

The 320 also includes convenient diagnostic features: an audible alarm which indicates when the water trap is full and a clear color indicator for gas sensor diagnostics and monitoring. Another useful feature of this analyzer is the inclusion of both Bluetooth connectivity and a USB for transferring combustion test data to a PC, giving techs flexibility when it comes to test data management.

The Testo 320 Combustion Analyzer Kit for Residential and Commercial Applications (P/N 0563 3220 70) is the base 320 kit and comes with the 320 analyzer, a rechargeable battery, AC power supply, 10 spare particle filters, and a hard plastic carrying case.

Our Testo 320 Combustion Analyzer Kit for Residential and Commercial Applications (P/N 0563 3220 71) includes everything the base kit does, plus an IR printer and 6 rolls of long life thermal printing paper.

E Instruments BTU1500-1

E-Instruments’ BTU1500-1 is a residential and commercial combustion analyzer which distinguishes itself from similar offerings from Bacharach and Testo in a few notable ways:

Like comparable analyzers from Testo and Bacharach, the E-Instruments BTU1500-1 features Bluetooth connectivity, pressure and draft measurement ( 0 to +/- 80 inches of H2O) and a full-color screen.

With the BTU1500-1, E-Instruments is providing an analyzer which can cover both light and heavy commercial combustion analysis, as well as the residential segment. With a flue gas max temperature of 1830°F, a CO upper limit of 8000, and a hydrogen-compensated CO sensor, this analyzer is well-equipped to handle the full spectrum of commercial combustion appliances.

UEi C85

Whereas E-Instruments stands out by integrating a printer directly into some of its combustion analyzers, UEi stands apart by using its own Electro Optic Sensor (EOS) technology to directly measure CO2 using light, and from that and other values, calculates the O2 concentration in the flue gas. This is the exact opposite of what the rest of the industry does.

As a result, the EOS CO2 sensors have exceptionally long life, and the need for an O2 sensor and it’s periodic replacements are eliminated. This can add up to substantial cost savings over the life of the analyzer.

The UEi C85 Combustion Analyzer with Long Lasting EOS Technology is UEi’s analyzer for residential combustion analysis, and has a large 2-line backlit LCD display, internal storage for 20 measurements, and is back by a 5-Year limited warranty.

UEi’s C85 has a flue gas max temperature of 1112°F, a CO measurement limit of 2,000 ppm, and no ability to measure draft or pressure. Therefore, the C85 is best suited for only residential combustion appliance servicing and commissioning, just like Bacharach’s Fyrite Intech. Technicians should note that the C85 can handle CO levels up to 4,000 ppm for up to 15 minutes, although the measurement accuracy at those levels is not specified.

The C85 is a popular analyzer due to its affordability and low long-term cost of ownership (made possible by UEi’s EOS technology).

Popular Combustion Analyzers for Commercial Applications

Compared to the residential segment of the combustion analysis market, analyzers for the commercial segment need to handle the higher temperatures and concentrations of CO generated by commercial furnaces, boilers, water heaters, kilns, and other combustion equipment.

In addition, there are more substances in the flue gas which need to be measured: NO, NO2, SO2, and unburnt combustibles often also need to be checked due to regulatory requirements. Thus, commercial analyzers will include or have the option of field installing sensors for these. Hydrogen-compensated CO sensors is another feature common among commercial analyzers, as are features which protect the analyzers’ electrochemical sensors from overexposure to the gases they’re designed to measure.

The range of fuels used in commercial combustion equipment is a bit broader than in the residential market, and that’s reflected in the number of fuels pre-programmed into commercial analyzers.

We’ll now discuss the commercial combustion analyzers most often bought by HVAC techs.

Bacharach PCA400

Bacharach’s PCA400 combustion and flue gas analyzer is intended for both commercial and industrial combustion analysis, and can be configured with up to four gas sensors (one of which would have to be O2). Technicians can fill the remaining three slots with:

The PCA400 can automatically dilute with ambient air the flue gas sample pulled into the analyzer, protecting the sensors from high concentrations of CO, NO, NO2, and SO2. This prolongs the working life of the sensors.

One last feature of PCA400 worth mentioning is the analyzer’s use of near-field communication (NFC) to reduce the time needed to swap out sensors in the field and resume testing. Each pre-calibrated B-Smart sensor stores its serial number and calibration curve. When one of these sensors is brought near the PCA400, a NFC reader built into the analyzer instantly downloads this information. From there, the tech just needs to physically replace the old sensor with the new one.

NFC isn’t the only wireless technology incorporated into the PCA400. This analyzer uses Bluetooth for transferring saved test data and real-time streaming of measurements in progress. The analyzer’s USB port can also be used for downloading saved test data to a PC. This combination of Bluetooth and USB is common in commercial analyzers.

E Instruments BTU4500

Continuing the trend of 4 sensor slots is the BTU4500 from E Instruments. The optional gas sensor choices are similar to those available for Bacharach PCA400:

As for sensor protection, the E Instruments BTU4500 uses a dilution pump to protect its H2-compensated and NOx filtered CO sensor while also extending its range of from 8,000 ppm to 50,000 ppm.

Like the Bacharach PCA400 and unlike the UEi C257, the BTU4500 has a full color graphic display and an interface navigated by buttons. This analyzer also has internal memory space for 2000 test results, and includes both Bluetooth connectivity and a USB port for transferring saved test data.

The BTU4500 is actually meant for both commercial and industrial combustion analysis. As a result, this analyzer comes with the choice of three different flue gas probe options. One of them is a high temperature probe (max of 2190°F) meant for the hotter exhaust gases of industrial combustion equipment.

UEi C257

The C257 from UEi is aimed at industrial combustion analysis, but is commonly bought for servicing commercial equipment. This analyzer features a 10,000 ppm max CO measurement limit, H2-compensated CO sensors, and 8 pre-programmed fuels.

The UEi C257 can withstand CO levels as high as 20,000 ppm for as long as 15 minutes, although the measurement accuracy at this concentration is not specified by UEi.

The UEi C257 also utilizes the same EOS technology as UEi’s residential and commercial analyzers. As a result, there is no O2 sensor to replace, and due to the optical operation of the CO2 sensor, that sensor will rarely need to be replaced.

The C257 also includes an NO sensor, enabling this analyzer to calculate the total NOx (NO and NO2) concentration in the flue gas.

Unlike the other popular commercial analyzers, the C257 doesn’t have an USB port or Bluetooth, the display is a backlit monochrome LCD with two lines of information instead of a color screen, and a rotary dial is used instead of buttons or a touchscreen. On the other hand, these design choices may explain why the C257 is significantly more affordable than the other analyzers mentioned here.

Wohler A450 (model 8390)

The A450 combustion analyzer from German manufacturer Wohler has a few notable differences from the other analyzers we’ve discussed above, chief among them:

Something else which sets the Wohler A450 apart is the 5” high resolution color touchscreen, which can display up to 14 measurements at the same time, providing almost all the information an HVAC tech could need at a single glance.

The Wohler A 450 features an integrated combustion tuning guide, which suggests relevant steps for quickly tuning the combustion appliance for optimal safety and efficiency.

Finally, the A450 can store 1000 test records, has a flue gas temperature limit of 1472°F, a CO upper limit of 10,000 ppm, and comes pre-programmed for natural gas, fuel oil 2, fuel oil 4, fuel oil 6, bio-fuel, LPG, propane, kerosene, digester gas, coal, and wood pellets. Users can define an additional four other fuels.

Popular Combustion Analyzers for Industrial Applications

Industrial combustion analyzers are designed to measure the level of several substances in the exhaust gas simultaneously. Thus these analyzers are built to use more sensors than either commercial or residential meters.

Just as technicians in the residential and commercial segments of the combustion market have their favorite analyzers, there are two industrial-grade analyzers which techs prefer over other options: Bacharach’s ECA450 and the UEi K945.

Bacharach ECA450

The ECA 450 from Bacharach can have up to seven sensors installed, with an O2 and hydrogen-compensated, low-range (up to 4000 ppm) CO sensor installed by default. Optional sensors include: high-range (80,000 ppm) CO, NO, NO2, SO2, and combustibles. This analyzer is pre-programmed with 10 fuels.

The Bacharach ECA450 features two built-in pumps: one for drawing in the flue gas sample into the analyzer and another for purging the low-range CO sensor when CO concentrations surpass 4000 ppm.

Since this analyzer is aimed for environmental compliance testing (as well as routing combustion equipment tuning and service), the ECA450 complies with CTM-030, SCAQMD, and other relevant test methods and protocols.

UEi K945

The UEi K945 is a four gas industrial analyzer, with an O2 and hydrogen-compensated CO sensor already installed. Unlike the Bacharach ECA450, the UEi K945 is a handheld analyzer.

The standard CO sensor has an upper limit of 10,000 ppm, but a high-range (and not H2-compensated) CO sensor with a 10% max is an option. Other optional sensors include:

The K945 is pre-programmed with 11 fuels (the user can define two more) and features a fluroplastic-lined flue probe.

How to Select a New Commercial Combustion Analyzer

HVAC techs looking to purchase a new commercial combustion analyzer today stand to benefit from a myriad of recent advances in flue gas component detection, electronics miniaturization, and analyzer component reliability. In addition, the combustion analysis industry is mature, with several manufacturers offering commercial combustion analyzers at different price points.

But how should a contractor weed through all the choices available on the market today?

The first step is to clearly identify the regulatory emission requirements applicable in your state or city, your budget for the new analyzer, and the needs and wants you hope the new commercial analyzer will fulfill.

With a clearer picture in mind, you can then sift through the offerings on the market by evaluating how each analyzer’s features meets your requirements. We’ve identified 8 classes of features to help technicians select the best commercial combustion analyzer for them.

1. Accuracy & Precision

First and foremost, a combustion analyzer is a measurement device whose readings (e.g. ambient CO concentration) have a direct impact on human safety. The tuning and repair actions initiated due to those readings can also lessen the environmental impact and improve the operational efficiency of the combustion equipment being serviced.

Consequently, measurement accuracy and precision are the basic requirements of any analyzer. These specs are always documented in the analyzer's user manual, which can usually be downloaded from the manufacturer's website or that of a distributor.

When reviewing those specs, pay particular attention to how the documented accuracy and precision vary over the entire range of the quantity being measured. For example, a combustion analyzer may have a "sweet spot" in the middle of its flue gas CO measurement range, with accuracy drifting off at both the low and high ends of that range.

2. Measurement Ranges

HVAC techs in the market for a new commercial combustion analyzer should know what the measurement ranges they need for flue gas CO, flue gas temp, and for whatever exhaust gas components they need to measure (NO2, NO, SO2, unburnt combustibles, etc . . .). Ditto for draft measurements and differential pressures.

Here are a couple suggestions:

3. Total Cost of Ownership

Investment in a commercial combustion meter goes well beyond the intial cost of the analyzer kit itself. There are also sensor replacements, periodic recalibrations, the (hopefully rare) repair, and consummables like particulate filters and rolls of thermal printing paper.

Like all other business decisions, deciding which analyzer to buy and what accessories (like additional probes for combustible gas leakage detection or differential pressure) to purchase with it involves weighing the costs against the benefits those purchases bring.

Advances like long-life O2 sensors and automatic sensor protection (see below) incur more upfront cost, but may save money down the road due to fewer sensor replacements and equipment downtime.

4. Display and User Interface Controls

Commercial analyzers measure & calculate plenty of readings, and have many options and test modes. Being able to efficiently select and utilize them is key.

Some techs will prefer a simple backlit LCD screen with buttons below it to navigate the analyzer modes and the display options. Others will opt for an analyzer with a large, full-color touchscreen which presents a lot of information in one glance.

Either way, the screen and analyzer user interface (UI) should be bright, clear, and easy to navigate.

5. Power Options & Battery Runtime

Most commercial combustion analyzers on the market today are handheld devices powered by internal batteries. Those batteries are usually either rechargeable Lithium-ion or the disposable (alkaline) variety. Running the analyzer from an AC power cord is sometimes an option too.

Closely related to an analyzer's power source is its runtime on fresh batteries or a full charge. Some analyzer features, like flue gas dilution pumps or sample conditioners, consume enough power to significantly lessen this operational time. If you plan on using those features frequently, assume on experiencing the lower end of the manufacturer's stated runtime.

6. The Ability to Easily Add and Swap Sensors in the Field

An increasingly standard feature of combustion analyzers is the use of electrochemical gas sensors which can be installed in the field. The ability to replace an analyzer's installed sensors with another combination when needed allows one analyzer to cover a wide range of combustion analysis needs. Simple tuning or checking may require just O2 and CO sensors, while a more environmental-focused analysis may require those two plus SO2 and NO.

Our recommendation is to purchase a commercial analyzer with at least two sensor slots in addition to O2 and CO.

The analyzer manufacturers are actively innovating in this area to make the sensor install and replacement process much quicker and easier for the tech. They may charge a premium for those innovations, but it pales in contrast to the cost of buying another analyzer.

7. Connectivity & Software

With the addition of Bluetooth and even WiFi, the analyzers on the market now are versatile, connected, industrial devices. Some connect wirelessly to the cloud, the technician's smartphone or tablet, or both. This connectivity pairs with manufacturer-supplied software to enable real-time test data to be streamed from the analyzer to the tech in a different room, and even enable the tech to operate the analyzer from his or her own Android or iOS device.

This technology gives the professional the option to store customer test data in the cloud, email detailed test information to the customer, and print custom reports.

Besides this new wireless connectivity, USB has become standard for commercial analyzers. With USB, a tech can take the analyzer back to the shop at the end of the day and download all the test data from the analyzer's internal storage for further analysis.

The ability to remotely operate a combustion analyzer can save HVAC pros a lot of time, since they can conduct a test on one piece of equipment while performing another task in another part of the building. That's why we recommend purchasing an analyzer with wireless (either Bluetooth or WiFi) connectivity, especially since many of the major analyzer manufacturers offer it.

8. Advanced Sensor Features & Sensor Protection

Finally, when shopping for a commercial combustion analyzer, we suggest buying one with the following features which boost sensor performance in addition to protecting both the sensors and the analyzer:

By weighing the pros and cons of each of these classes of features, HVAC pros can make the commercial combustion analyzer purchase which is best for them.

CO - Carbon Monoxide and Combustion Analysis

What HVAC Technicians Need to Know About Carbon Monoxide?

The first and foremost goal of an HVAC technician is to ensure the safe operation of the equipment they are working on. Both the safety of the customer and of the tech take precedence over other goals such as efficiency and cost savings for the customer.

What is Carbon Monoxide?

In the HVAC industry, carbon monoxide (CO) is one threat to that safety. CO, like soot, is a product of the incomplete combustion of carbon-containing fuels such as natural gas, propane, wood, charcoal, and oil. Unlike soot, CO is a colorless, odorless, toxic gas.

Since CO is created via incomplete combustion, minimal CO is produced when combustion is occurring at maximum efficiency. In fact, this is one of the key reasons why combustion analysis is performed: it both reduces fuel costs by ensuring peak appliance efficiency and reduces the risk of CO poisoning.

The Silent Killer

But why is CO poisonous? The answer comes down to biochemistry.

Hemoglobin is the iron-containing protein in red blood cells which allows the body to absorb oxygen from the air and transport it via the circulatory system to all the cells which need it.

CO binds to hemoglobin 300 times as well as oxygen does, and while CO is bound to hemoglobin, the protein can’t absorb and transport oxygen. When too many hemoglobin molecules are rendered useless by CO, the body experiences a lack of oxygen, which can cause many symptoms and even death.

What CO Levels are Dangerous?

Generally, prolonged exposure to CO levels in the air from 1 to 170 parts per million (ppm) does not cause symptoms in humans. For some individuals, especially those with heart issues, exposure at these levels can produce chest pain. Above 70 ppm, symptoms includes nausea, fatigue, and headache. Prolonged exposure to CO levels above 150 ppm can cause disorientation, loss of consciousness, and death.

What symptoms an individual will experience at a given CO level depends on the length of that exposure, level of exertion, altitude, as well as that person’s cardiovascular health. Any heart disease—diagnosed or not—will increase a person’s susceptibility to CO poisoning. This fact was cited in an unsuccessful attempt by OSHA to substantially lower the acceptable limits for workplace CO exposure.

Relevance for HVAC techs

As an integral part of their job, HVAC technicians work closely with CO sources (such as gas-fired water heaters, furnaces and boilers) which may or may not be operating safely, in enclosed areas. These are all reasons why techs need to stay alert to the danger of CO and make safety a priority in every service call.

That’s why technicians need to perform ambient and flue gas CO tests with their own calibrated equipment as soon as they arrive at the combustion appliance. Many of the combustion analyzers and standalone hand-held CO monitors on the market today won’t turn off if the CO level detected is at a unsafe level, which keeps the tech alert to the ongoing danger. Another safety feature these tools have is excellent CO sensitivity down to the single digit ppm CO range, which enables the tech to tune the appliance for the absolute lowest possible amount of CO in the flue gas. Together with a strong, reliable draft of the exhaust gas, minimizing the CO content in the flue gas is critical to preventing CO levels around the appliance from accumulating to dangerous levels.

Although many jurisdictions have rules mandating the number and placement of residential CO alarms, an HVAC tech shouldn’t rely on them for either their safety or that of their customers, as an installed alarm could be expired, its battery could be drained, or there might not even be one near the appliance where the tech is working.

CO poisoning is a real danger anytime combustion occurs in an enclosed space, but by making ambient CO measurement and reduction the #1 priority at every jobsite, HVAC professionals can prevent a potentially deadly exposure for every customer, while improving the efficiency of their furnace, boiler, or water heater.