Q1: What are some of the factors that need to be taken into account when assembling a gas detection and monitoring system?

The most critical factor is selecting the appropriate sensor technology. However, you must also determine sensor quantity, sampling location, alarm functions, and display requirements.

Q2: What types of combustible gases will the sensors detect?

Combustible gas sensors are non-specific and theoretically will respond to all combustible gases and vapors. The sensor response produced by a particular gas will be determined in part by the fuel value or "heat of combustion" for that gas. Heats of combustion can vary from one combustible material to another.

Q3: What is the best location for a sensor?

There are many variables that must be taken into account when choosing a location for your sensor. A general guideline is to place the sensor in a location where the air currents contain the maximum concentration of the gas you wish to monitor. This means being careful to not place the sensor too far away from any potential source of escaping gas. All sensors must be installed within the specified temperature range, keeping in mind the ambient temperature limitations. For vapors and gases three or four times heavier than air, sensors are best located near the floor. For detection of gases lighter than air, ceiling location is best. Sensors should be mounted between a source of ignition and a potential leak source. It is best to anchor the sensor to a base or wall where they can be protected from direct contact with water, immersion and damaging vibrations. It is also important to make sure your sensor is accessible for monitoring and calibrating purposes.

Q4: What is the expected life of a sensor?

Expected life may differ depending on each gas monitor’s operating environment. See the product specifications for a more detailed description.


Q1: Why are there four different models of the PrevEx® flammability Analyzer?

Providing four different models allows the buyer to purchase an analyzer specific to their needs and situation. Since an analyzer must always be hot enough to keep all vapors in the sample stream above their flash points, the varying temperatures require different construction and sampling systems.

Q2: How do I determine which model PrevEx® is right for my application?

Complete and submit the Application Survey.

Q3: The air in my dryer is heated to 200°F. Does that mean that I need a model SNR672 PrevEx® analyzer heated to 248°F?

The goal is to keep all vapors above their flash points as they travel through the analyzer and sample tubes. Meaning it is not always necessary to heat the analyzer to the same temperature as the sample. For example, a process containing only Acrylic Acid needs a sample train heated to at least 130°F, which is the flash point of Acrylic Acid plus a few degrees safety margin. In this particular case, after careful review of the application survey, we might confirm the need of a model SNR671 analyzer heated to 140°F.

Q4: The flammability of a substance varies with its temperature. Doesn’t an analyzer have to be as hot as the source to measure true flammability as it exists at the sample point?

No, not if the analyzer allows for the temperature difference. PrevEx® analyzers are calibrated for an oven temperature of 400°F, however, calibrations to suit higher or lower sample temperatures are available.

Q5: How large is the optional outdoor housing?

There is no size difference. For outdoor use, a corrosion-resistant stainless steel and coated aluminum housing replaces the standard housing.

Q6: Why are the PrevEx® analyzers designed to mount directly on the process or duct?

By mounting the analyzer directly on the process or duct the fastest possible response time is provided. Possible sample dropout is also eliminated. For further clarification see application note H7APP020, The Importance of Response Time When Measuring Flammable Vapors in Process Ovens and Dryers.

Q7: My drying oven has three zones, each with its own exhaust. All three exhausts join into a common duct going to our fume oxidizer. Can I use one analyzer sampling the common duct rather than a separate analyzer on each zone?

No, the use of one analyzer is not appropriate and the reasons are two-fold. First, an analyzer on the common duct will monitor the exhaust stream going into the oxidizer but it can’t measure the concentration of flammable vapors from an out of control oven zone. This is because the other zones will dilute the exhaust from the dangerous zone prior to reaching the analyzer. Second, the national safety standards applied in this particular process mandate the use of an analyzer on each individual zone.

Q8: What happened to the Control Instruments type FFA and FTA flammability analyzers? Why can’t I find them on the web site?

The type FFA and FTA flammability analyzers were retired from the product line after the introduction of the PrevEx® analyzers. The conversions are as follows: Discontinued Replacement FFA model SNR144 PrevEx® SNR671 FTA model SNR500 PrevEx® SNR672 or SNR674 FTA model SNR550 PrevEx® SNR675


Q1: Do I need to go to the sensor in order to operate the monitor?

No, the SmartMaxII monitor can be located away from the sensor point at a safe location.

Q2: Can I connect different types of sensors to the same SmartMaxII monitor?

No, the SmartMaxII monitor can only be connected to one type of sensor, either the catalytic or electrochemical sensors. In the case of the electrochemical sensor the types of gases can’t be mixed on the same SmartMaxII monitor.