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    Very accurate for the price. Every Inspector is carefully calibrated before shipment.  The LCD display has a resolution of 1ppm.  Generally speaking the accuracy is +/-10%, (e.g. a reading of 100ppm will be displayed when the concentration reaching the sensors is 90-110ppm). At concentrations lower than 20ppm, the accuracy is +/-2ppm.   

    Simply press the MAX button, an arrow over the MAX sign indicates MAX mode is active. Suppose you are curious about the maximum carbon monoxide level that you are being exposed to by exhaust from vehicles when you walk down a city block. 

    If you wear the Inspector with MAX mode active, you'll find out.  Perhaps you wish to sample the exhaust from your chimney, furnace or hot water heater. The MAX mode is perfect for this because the concentration will change due to the air mixing. 

    Operating in MAX mode is almost always preferable when you use the hand aspirator pump. In professional applications the norm has been an electronic sampling pump to draw a sample from a remote location.  These pump with their high power, cost and long lengths of tubing are very cumbersome.  In many cases, you can use the MAX mode to eliminate the need for that annoying motorized pump.  By operating in MAX mode, you can simply tie a lanyard or rope to the Inspector clip and lower the unit into the area of interest. Simply wait about 1 minute and then pull it back and view the reading.  All this talk about pumps brings us to the next FAQ.

    A pump is not required and it is only needed for drawing remote samples (e.g. from an exhaust stream or reaching the ceiling). You can't shove the Inspector itself into a hot exhaust stream, but you can draw a sample to it with a pump. 

    Sensorcon sells the Carbon Monoxide Inspector Kit. This kit includes the carbon monoxide Inspector as well as a robust carrying case and a hand aspirated pump.  Hand aspirated pumps use rubber bulbs to draw an air sample from the end of a stainless steel probe, down a hose, through a filter and to the Inspector's sensor. With a pump, you can quickly draw in air from the ceiling, behind a stove or in your immediate area as you walk through a building.  This allows you to quickly assess the carbon monoxide concentration throughout a large area. 

    We like using the MAX mode for a lot of these scenarios. Motorized pumps offer a more steady airflow than the pulses you'll get with a hand aspirator. Although motorized pumps consume a lot of power and cost much more. You'll be able to perform almost all of the tasks you can do with a motorized pump and at a much lower cost with a hand aspirated pump used in combination with the Inspector's MAX mode.

    Although that's not what our engineers had in mind, however you can if you really want to. 

    Please Note: The alarm in the carbon monoxide Inspector is not nearly as loud as traditional CO detectors. Instead of mounting the Inspector on the wall, we suggest setting it on your night stand when you are not carrying it around.

    The Inspector is not like lower cost carbon monoxide detectors. The Inspector is a professional grade portable CO detector, you can carry it, clip it on your clothing or place it anywhere you wish.  Lower cost wall mount detectors are not as accurate as the Inspector and most of them have alarms that won't sound for very long periods of time. The Inspector will alarm immediately sound off when the carbon monoxide concentration exceeds 35ppm.  This leads us to the next FAQ:

    The Inspector is a tool for measuring actual carbon monoxide concentrations and alarming above 35ppm.  Lower cost CO detectors are only meant to sound an alarm when carbon monoxide concentrations are elevated for extended periods of time. 


    Please Note: We're not on a crusade to eliminate lower cost carbon monoxide detectors. They are typically good for sounding an alarm in homes where healthy people live.  The Sensorcon Inspector can be thought of as a supplement or diagnostic tool.  If you think there might be carbon monoxide present, but a lower cost alarm didn't sound then our Inspector will alert you.

    Most lower cost alarms will only sound off after 15 minutes (or in some cases hours). However, you can use the inspector to get instant readings. The Inspector is currently in use by many EMTs and fire departments.  HVAC technicians and home inspectors also use the Inspector on maintenance calls. 

    The bottom line is that the Inspector is more expensive than the $20-$50 you'll pay at a local hardware store. However, you'll be getting a professional grade American made instrument that is easy to use and suitable for giving you real carbon monoxide concentration information.

    You probably don’t need to worry at concentrations of <5ppm, just keep an eye on it.  Although, you'll probably need to investigate further at higher concentrations.

    The Inspector combines a rugged, compact, quality design with excellent ease of use at a low cost. There are three kinds of portable carbon monoxide detectors sold on the market today:

    Diagnostic CO Detectors:  These are usually fairly large devices sold by Bacharach, Fluke, UEI & others. In most cases they have poor battery life and are not water resistant.  They are fairly easy to use and most have a MAX mode, require occasional calibration, and typically cost $200 to $400. Support for these products is virtually nonexistent and since the companies that sell them generally don't manufacture them. Sensorcon's carbon monoxide Inspector is made to the highest quality in the USA. It is rugged, waterproof, has a standard battery that lasts for years and is fully supported by our knowledgeable staff.

    Safety Carbon Monoxide Detectors: These are compact devices sold mainly by large gas detector companies for around $100 to $400. These companies are concerned with selling high volumes to large mining or industrial operations and they require frequent calibration. Sensorcon's carbon monoxide Inspector is just as small and robust as these safety oriented CO detectors. However, it is much easier to use. Sensorcon's support staff will answer any questions or concerns. We're not just making products for large companies. If you're a one man shop or just an average consumer that wants better information about carbon monoxide, we're here for you too.

    Carbon Monoxide Analyzer: If you see the word "analyzer" it usually only means you will pay more. This being for  the same technology and only a more fancy looking device.  Maintenance issues are much higher.  You can use our carbon monoxide Inspector for almost any application that you can use an analyzer for in measuring CO. As long as you are interested in ppm resolution over a 0-2,000 ppm range. 

    This frankly covers about 90% of the applications.  Any analyzer in this range that uses an electrochemical sensor will not beat the Inspector's performance. If you are considering buying an expensive analyzer then please compare the specs to our carbon monoxide Inspector before you make your purchase.,

    Feel free to contact us with any questions.  

    Most likely there's an interfering gas and or vapor present. The sensor used in the Carbon Monoxide Inspector was designed to be as selective as possible to CO. This meaning it should respond to carbon monoxide and nothing else.

    The most common interfering gas is Hydrogen with an ~10-15% cross sensitivity.  What that means is that if the carbon monoxide inspector is exposed to 100ppm of Hydrogen, it will display 10-15ppm.  The most common place we've found hydrogen is human flatulence. Which in some cases can be composed of several % hydrogen. 

    10,000ppm = 1%.  (1% hydrogen would lead to a response of ~10,000ppm X 10%, or 1,000ppm, 2% hydrogen would likely cause the Inspector to display OL for overload as the max value is 1,999ppm).

    Other gases like methane will not cause the carbon monoxide Inspector to respond.  Alcohols should not cause the carbon monoxide inspector to respond unless there is a significant amount near the gas sensor inlet.  So, if you clean the face of the inspector with a little alcohol it shouldn't respond. If you have any questions about the readings you are getting, please feel free to contact Sensorcon.  We'll do our best to help you figure out what's happening.

    Carbon Dioxide (CO2) is NON-TOXIC, Carbon Monoxide (CO) is TOXIC. The CO Inspector measures Carbon Monoxide (CO) and not Carbon Dioxide (CO2). We hear a lot of customers and stores mix up CO & CO2. The key difference is that CO only has 1 oxygen atom, and CO2 has 2 oxygen atoms.

    CO really wants to be CO2.  If it can't find a 2nd oxygen to cling to thenit will try to cling to something else. If you breathe in carbon monoxide it will cling to the hemoglobin in your blood. Your hemoglobin normally likes to stick to oxygen too but can't with carbon monoxide around.

    This is why carbon monoxide is toxic and it prevents your blood from clinging to oxygen. CO2 on the other hand, is what we exhale.

    Both CO and CO2 can be formed by burning things: Whenever anything with carbon in it burns, it reacts to the oxygen from the air to form CO & CO2. Ideally only CO2would be formed. In the real world, chemical reactions are never ideal. Burning is no exception. If any part of the fuel is burned with too little oxygen then it will form Carbon Monoxide (CO) rather than Carbon Dioxide (CO2). This is why the carbon monoxide Inspector is useful for so many applications including anywhere there is a flame and a chance for CO to be present.  


    When shipped, our meters are calibrated and tested to read within +/-10% of the calibration gas applied.  This accuracy normally lasts 6 months. Under normal use, expect the accuracy to drift by ~10% for every 6 months it is not calibrated. With this in mind, we have different recommendations for different applications.  A list of applications of increasing demand is below.

    The Average Property Owner:  If you just want a rough idea of how much carbon monoxide is present around the house or you want to use the Inspector to find other CO sources. Then calibration is not normally required for 2 years of use.  We recommend calibration or replacement after 2 years.


    General Purpose Professionals:  If you are a professional Home Inspector, HVAC Technician, Fire Department, EMT, or in a related field then we recommend calibration every 6 to 12 months to maintain the approximate +/-10% accuracy specified.  Exposure to fluctuating temperatures and humidity by leaving the device in a vehicle outside can cause the sensor output to change over time. This includes inaccuracies increasing the longer it has been since the last calibration.

    Precision Professionals:  If you demand the highest accuracy, (+/-10% or less) for applications like combustion analysis, energy audits, or medical applications then we recommend a calibration every 3 to 6 months.

    Safety Applications:  If you are planning to use the carbon monoxide Inspector for "mission critical" safety related applications, then you are probably obligated to follow standards set by OSHA or another agency. This will often call for bump or calibration testing every week or month.  In these cases you should follow whatever standards you are obligated to follow.

    How Is Calibration Done:  You can send it in to Sensorcon for calibration for a $39 service fee or do it yourself if you have calibration gas & a regulator with tubing.  We offer calibration gas accessories in our web store. 

    If you'd prefer to do it yourself then simply hold down both buttons for 5 seconds to enter CAL mode. Then press the right button to zero for 30 seconds. Finally, apply the gas to the sensor port for 1 minute, and you're done. Our Inspector will automatically adjust itself accordingly.

    Years, unless the alarm is set off on a continuous and repeated basis. The alarm condition consumes much more power than when the device is not in alarm. The flashing LEDs and buzzer use much more power than the sensor and LCD display.  Normally, the Inspector's battery should last 2 to 4 years. If the alarm is active on a regular basis then it can drain the battery much sooner. If you ever need to replace the battery it uses 1 standard CR123A Lithium battery.

    The Inspector requires little to no maintenance. The average consumer won't have to do any maintenance.  Professionals requiring high accuracy will simply need to perform occasional calibration.  We also have service plans that eliminate down time and maintenance for such professionals. If you have any further questions please do not hesitate to contact us for more information.