Do LEL sensors have a cross interference to CO2?

A career firefighter and great friend of Industrial Scientific passed this video clip on to me this week.

Firefighters in Phoenix, AZ were called to an incident at a fast food restaurant after a worker had collapsed walking up the stairs from the basement.   The firefighters, after almost being overcome themselves, were surprised to see high …

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AskDave Live at NSC in Philadelphia

If you are attending the National Safety Council Congress and Expo in Philadelphia this week, stop by the Ventis Diner at Industrial Scientific, Booth 1323.  Bring your questions to AskDave live at the booth from 3:30 – 6:00 on Monday afternoon and from 10:30 to 1:30 on Tuesday.

I would love to get a chance to meet …

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Baby it’s cold outside…

Cold winter temperatures have set in over most of the northern hemisphere and with them come some differences in the way your portable gas monitoring instruments function.  The low temperature rating  for continuous operation of most Industrial Scientific portable instruments is -20 degrees Celcius.  However, they may be used at lower temperatures for intermittent periods.  …

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ISC & Predictive Solutions Presentation at NSC

Next week at the National Safety Council Congress & Expo my colleagues, Dr. Raghu Arunachalam, Griffin Schultz from Predictive Solutions, and I will be giving a presentation entitled Using Data to Drive Change in Your Safety Culture.

The presentation will be from 1:30 to 3:00 on Monday, October 31, in Room 113A of the Pennsylvania …

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Why do I see negative readings on my gas monitor?

This is a common question that is frequently asked by customers.  As recently as today in fact.   So, why do you sometimes see negative readings on your gas monitor?

All electrochemical or catalytic gas sensors can be prone to both positive and negative drift due to environmental factors such as changes in temperature and humidity. …

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Do LEL sensors have a cross interference to CO2? AskDave Live at NSC in Philadelphia Baby it’s cold outside… ISC & Predictive Solutions Presentation at NSC Why do I see negative readings on my gas monitor?

May
15

Ventis MX4 Recieves New Certifications for Underground Mining

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Industrial Scientific’s Ventis MX4 multi-gas monitor now has certifications that expand its use into underground mining applications around the world.

The Ventis MX4 is now certified by MSHA for use underground in the United States, by the China Mining Association (China MA) for use in mines throughout China and in accordance with the ATEX standards for M1 equipment used in mines that follow the European standards.

The Ventis MX4 is a small, lightweight 4-gas monitor that is ideal for use by the everyday miner.  The ability to detect methane, oxygen, carbon monoxide and nitrogen dioxide or hydrogen sulfide simultaneously allows the Ventis MX4 to provide the protection from gas hazards that every miner needs.

If you are working as an underground miner in any of these regions, you can now entrust your gas safety to the Ventis MX4!  I know that I would!

Keep Safe!

Dave

 

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Apr
04

Should I use a pump with my portable gas monitor?

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Portable gas monitoring instruments are typically operated in a passive (diffusion) mode or in an aspirated (pumped) mode.  How do I know which one I should use and whether or not one mode is better than the other?

This is a common question that really has a simple answer, but it does come with some detail.

Most sensors intended for use in portable gas monitoring instruments are designed to operate in the passive mode.   These designs are such that gas in air diffuses through normal air currents into openings on the face of the sensor and accumulates on and reacts with the sensor’s working electrode.   The sensors will function and perform normally in a properly designed diffusion based instrument with no help from a sampling pump at all.

However, there are many that believe that a pump is necessary to draw air into the instrument and sensors and that an instrument with a pump can detect gas in a wider area than a simple diffusion monitor.   These are simply myths of gas detection and the true fact is that the flow rates of pumps used with portable instruments are so relatively low that the only gas that is sensed or air that is drawn in is from the immediate end of the sampling hose or inlet of the sampling pump.  Truly whether the instrument is operated in a diffusion mode or in a pumped mode, it is only a point detector and can only detect gas that is at the immediate face of the sensors or inlet to sampling pump.

So exactly when should I use an instrument with a sampling pump?   As I said earlier, the answer is quite simple.  The only time that it is necessary to use a sampling pump with a portable gas monitoring instrument is when it is necessary to sample the conditions of the air in an area located remotely from the location of the instrument.  Confined space regulations require that atmospheres of confined spaces are tested prior to entry and to do that requires a pump to draw the air from within the space out to the instrument.

The rule of thumb then for whether or not you need to use a pump with your instrument is simply that  if you are standing at Point A and need to know the gas concentration Point B, you need a pump.

Dave

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Mar
07

Why does my MX6 go into PUMP FAULT during calibration?

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MX6 user Mike asked a question about a scenario that may be frequently encountered while calibrating an MX6 or any aspirated (pumped) gas monitoring instrument.  His question was as follows:

“Problem: Pump faults when test gas is applied. Tried turning gas on before connecting sample hose. We have two of these models. First one calibrated fine, but the 2nd one continues to have pump faults each time the test gas is applied. Any suggestions?”

These circumstances will most often be seen when attempting to calibrate the instrument with a cylinder and a fixed flow regulator with an on/off valve.  If the positive flow from the regulator does not match the flow of the pump, the pump itself and the internal flow/pressure monitoring system will be over-pressurized causing the pump fault condition to occur.

There are two simple solutions to this problem.   You can calibrate the instrument successfully with a fixed flow rate regulator by placing a simple T-fitting in the gas line between the regulator and the pump inlet of the instrument.  The gas flow rate from the regulator should be greater than the flow rate of the instrument pump.   In this scenario, the excess gas flow and pressure will be vented to the atmosphere through the open end of the T-fitting while the pump draws in the amount of gas it needs.

The second solution to this problem is to use a demand flow regulator.  A demand flow regulator is designed and recommended for calibrating  a pumped instrument.  The pump will draw only the gas sample that it needs from the cylinder at the proper flow rate without wasting any gas.   Although the demand flow regulator is typically double the price of the fixed flow regulator, the cost of the gas savings when using the DFR will quickly make it more econmomical.

Of course, even when using a demand flow regulator, a blocked calibration gas line or any empty gas cylinder will still drive the pump into a fault condition. 

Calibrating your instrument properly is the first key to a successful gas monitoring program.  Using the right regulator makes calibration easy and helps you avoid all the PUMP FAULTS that can occur.

Until next time, Keep Safe!

Dave

 


 

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Feb
24

The Answer is Blowin’ in the Wind

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Industrial Scientific has recently identified an issue that may result when portable gas monitors equipped with sampling pumps are used to draw a sample from a confined space outdoors in conditions when wind speeds are greater than 5 miles per hour.   Under these conditions, the gas sample may be diluted by the excess air flow attributed to the wind and cause the instrument readings to be significantly lower than actual gas concentrations.   This condition, revealed during testing in our laboratories,  was found to exist in the Ventis instrument equipped with the remote sampling pump as well as in several other brands and models of gas detectors tested.  

As a result of these findings, the interface between the Ventis instrument and its remote sampling pump has been improved.  Please see the attached Technical Bulletin:   Use of Portable Gas Monitors with Pumps in Outdoor Environments

If you are using a portable gas monitor equipped with a remote sampling pump outdoors, you should take precautions to shield the instrument from the wind as much as possible in order to minimize the dilution effects on the gas sample unless you have assurance from the manufacturer of your particular instrument that it is not affected by these conditions.

So keep yourself safe, make sure your gas readings aren’t just blowin’ in the wind and consult your manufacturer to ensure that your instruments are safe to use outdoors in these “windy” conditions.

Dave

 

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Feb
13

What’s All This PEAK Reading Stuff About Anyhow?

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Recently customer Eli asked the question, “Why do I have to clear the peaks on my instrument?”  In fact, with full datalogging now being a dominant feature in most gas monitoring instruments,  manually clearing the peak reading registers isn’t as important as it used to be.   Nevertheless, why is it still a good practice to clear the peak reading registers of your gas monitor before use and just what is all this PEAK reading stuff about anyhow?

Gas monitoring instruments that have a PEAK Hold or a PEAK Reading function store the highest measured concentrations of combustible and toxic gases and the lowest measured concentration of oxygen.  If the design of the monitor follows the best practice, the PEAK reading registers will not be automatically cleared when the monitor is turned off.   This is to ensure that the peak reading values can be recovered and reviewed if any type of gas exposure incident occurs while  the monitor is in use.   It is important on the other hand to clear the PEAK reading registers before each days use because if they are not cleared, you will know what the highest readings were, but you will have no idea when they occurred.   They could have occurred yesterday, last week or even last month for all you know.

As I said earlier, the presence of a full datalogger in the instrument makes all this PEAK reading stuff a moot point.   Retrieval and analysis of the data from the monitor makes it easy to determine what the peak gas concentrations were and exactly when they occurred.  But if your gas monitoring instrument does have a PEAK reading feature, the best practice, even still, would be to ensure that the readings are cleared just prior to each use.

So clear the PEAKs before you go out to work and keep safe!

Dave 

 

 

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Feb
06

The Most Frequently Asked Question

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It has been almost three years since Industrial Scientific launched the AskDave portion of our website.   In the nearly 2000 questions I have answered since the beginning, there is one that stands out by far as  the most frequently asked.   Why is there no oxygen sensor showing up in my M40 display?

So, just what does happen to that oxygen sensor reading anyway?

The galvanic fuel cell oxygen sensor, like that used in the M40 and other similar instruments, is one of the only sensors that normally produces a signal larger than its baseline output in a clean air environment.  The M40 and other instruments that do not use  “smart sensor” technology rely on that signal to identify that the oxygen sensor is in place and properly installed in the instrument.  When the sensor reaches the end of its useful life, it no longer has any measureable output at all and therefore it has no way to identify itself to the instrument when the unit is turned on.   The end result is that the oxygen sensor disappears from the instrument display, simply because the instrument does not know that it is there.

Do not be alarmed by this condition.  The sensor cannot disappear from the instrument during use.  Oxygen sensors that lose their output during use will fail to a condition that puts the instrument in a  continuous high alarm state and will not leave you unprotected.

This is just another in the long list of reasons that you should verify visually that all of your sensor readings appear to be normal each time you turn your gas monitor on and bump test every sensor before use. 

Keep those questions coming and above all, keep safe.

Dave

 

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Jan
17

Just another reason to bump test your gas detector….

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For the first post of 2012, I thought that it would be appropriate once again to talk about bump testing.  But this time, I am going to venture away from looking at bump testing from the point of view that the only way you know that a gas sensor will respond to gas is to test it with gas.  I’ve recently learned of another reason why you should bump test your gas monitor regularly. 

Portable gas monitoring instruments typically are powered by some type of lithium battery.   Single gas instruments that are meant for long life typically utilize primary (non-rechargeable) lithium batteries and under normal operating conditions draw very small amounts of current from them.  During a normal chemical reaction that takes place in the battery during storage or under very small load conditions, a thin film of lithium chloride forms what is known as a passivation layer on the lithium anode of the battery.   This passivation layer serves to prevent the battery from self dishcharging and helps to maintain its overall life capacity during storage.

The down side of the passivation layer is that as it forms, the working voltage of the battery is reduced and its ability to deliver power to a high current load, such as your gas monitor going into alarm, is diminished.  As the passivation layer “burns” off, the battery’s ability to deliver the higher currents is restored.

So, one way to ensure that the battery in your gas monitor is properly conditioned and has the passivation layer depleted is to periodically force the instrument into the high current mode by bump testing it and activating the alarms.  In this case the bump test will tell you that the alarms are functioning properly and help condition the battery so that it can operate the alarms properly as it needs to if you encounter a dangerous concentration of gas in the field.

As I said, just another reason that bump testing your gas monitor should be part of your daily routine.

Here’s to a healthy and gas safe 2012!

Dave

 

 

 

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Dec
12

Baby it’s cold outside…

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Cold winter temperatures have set in over most of the northern hemisphere and with them come some differences in the way your portable gas monitoring instruments function.  The low temperature rating  for continuous operation of most Industrial Scientific portable instruments is -20 degrees Celcius.  However, they may be used at lower temperatures for intermittent periods.  The response of the sensor does change as the temperature gets colder but the response is compensated to cover the effects of the low temperature and keep your gas readings within +/-15% of the actual concentrations.

Here are some tips to help you get a warm feeling from your gas monitors when you are using them in out the cold.

1.  When you walk outside, you feel the cold instantly.  However, it will take a while for your gas monitor to reach equilibrium with the ambient temperature.  The temperature compensation will track with the internal temperature of the monitor.   If you are going to be using the monitor for 20 minutes or less, there is no reason to allow it to stabilize and adjust to the temperature before useing it.  Turn it on, take your readings and get back inside where it is warm.

2.  If you will be using your monitor outside for extended periods longer than 20 minutes, it  is best to let it stablize at the ambient temperature for 15 – 20 minutes before use and then turn it on and zero the sensors in fresh air.

3.  The response of the instrument will get sluggish at temperatures below -20C.  The display may get dim and even go blank if it freezes.  If this happens, your gas monitor will likely still detect gas and will still alarm.  If you have to use it this way, you should bump test it before each use to make sure it responds and  you should get your unit warmed up as soon as possible. 

4. The sensors in your instrument will start to freeze at temperatures below -20C for an extended period of time.  The oxygen sensor will normally be the first to freeze.  When frozen, the sensors will not be able to produce a reliable reading, but functionality should return once they warm up and thaw out.

5,  Battery run time will be reduced at low temperatures.   Below -20C  expect at least a 30- 40 percent reduction in run time.

6.  Keeping your gas monitor close to your body will keep it as warm as possible.  If you are using the monitor  for remote sampling, keeping it inside your coat as long as possible will help keep it warm and functioning longer.

A good rule of thumb for using your gas detector in cold temperatures is that your gas monitor can generally stand to be out and working  in the cold as long as you can.  If it’s too cold for you, it’s probably too cold for the instrument as well.

Baby it’s cold outside, so until the milder temperatures of spring return, work safe, and try to keep warm.

Dave

 

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Dec
05

25 Years of Gas Detection

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This past Friday, I celebrated my 25th anniversary at Industrial Scientific.   Wow!  What an opportunity to sit down and reflect on how the industry has changed over the last quarter century.

In the past 25 years we have seen gas monitoring instruments change from analog based meters with limited functionality to the feature rich microcomputer based machines of today.  We have built multi 5 and 6-gas instruments that are a fraction of the size of yesteryear’s single gas moniters.  We have moved from wireless communications interfering with our instruments being a primary reliability concern to embedding wireless communication in those instruments to give us real time data.   We have gone from having stacks of paper to document infrequent calibrations to using docking stations to test and calibrate routinely and document records automatically.  New sensing technologies such as PID and infrared have become commonplace in portable instruments.

Yet we still have work to do.   Workers still become injured and die in gas-related accidents.   I do not know what technology will bring to gas monitoring in the next 25-years, but I do know that we will have to compound the  advancements of the past 25 years more than once to totally eradicate gas related injury and death.

We will take a  look back again in another 25-years.   Hopefully we will see that we have succeeded with technology enough that we have made our own existence questionable.

Until then – think safe, be safe.

Dave

 

 

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Nov
15

To Calibrate or Not to Calibrate……

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For those of you who know me well, don’t be alarmed.   I’m not going to talk about bump testing today.  Today I’m focused on calibrating gas monitors.  Before you over react, yes, I am still committed to the importance of bump testing gas monitoring instruments.  But regular calibration plays a role that is just as vital.

Calibration establishes the accuracy of the sensors and the monitor that they are installed in.  It provides a reference point for the readings and a degree of confidence that the measured concentrations are in fact what the monitor says they are. 

So why does Industrial Scientific recommend calibrating instruments monthly when some others clearly say that longer intervals between calibrations are okay? 

Here it is.  Calibration is needed to ensure that your instruments perform within the stated specifications.  If the sensor manufacture states that the specified signal drift  of the sensor itself is +/-2% per month or greater, then it is clear that if you want to maintain an instrument accuracy of +/-5%, that the sensors must be calibrated at least no less frequently than every three months. Now when you take into account that the manufacturer’s specifications are based on laboratory conditions, and your instrument is used in a variety of changing and stressful environments and exposed to many performance altering physical factors, then clearly you must calibrate more frequently than that.

Our studies of sensors used in fielded instruments indicate that more than 50% experience changes in sensitivity of greater than 3% per month.  It then seems obvious that if you want your instrument to be accurate to at least +/-5% at any given time, that it should be calibrated on at least a monthly basis. 

You can check your instrument at various intervals to determine if it reads as accurately as it is supposed to.  But why do this and then make a judgement call as to whether or not it is good enough?  It will take the same amount of time and the same amount of gas simply to calibrate the instrument.   And the result sets and guarantees the accuracy.

In the end, if the most accurately reading gas monitoring instrument is what you seek, calibration is the only way to go.

Keep it safe, keep your instruments calibrated properly!

Dave

 

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