Critical Use and Design Factors in Carbon Monoxide (CO) Detectors, Monitors and Alarms, a White Paper

 
By James Wiebe

Brief Introduction of James Wiebe

I am the CEO of Radiant Technology, with 45 years of varied management and electrical engineering experience. I am also a passionate pilot and serial entrepreneur.  I am highly skilled in sensor design. A recent accomplishment which I am proud of was an airborne logging sensor package, done as a subcontractor on a USAF contract. 

Goal of this White Paper

In this paper, I am discussing the use and design factors in Carbon Monoxide detectors, monitors and alarms, hereafter referred to as "CO Detector". Use discussion of CO Detectors includes the background need along with the application of these devices. I also dig deeply into design and implementation issues. I provide comments as these factors relate to our new product, "CO Pro".

The Need for CO Sensors

Aircraft accidents caused by CO poisoning have documented by the FAA and by the NTSB. The FAA has prepared a helpful online brochure which is available at the following link:

Carbon Monoxide, a Deadly Menace

Where the FAA shares the accident of a Piper Comanche 400 piloted by Dr. Robert Frayser. The accident resulted after he'd taken off and was flying from North Bend, KS to Topeka, KS.  In dramatic fashion, he awoke inside his wrecked aircraft in a hay field, thinking he was still in cruise flight. In actuality, he had been poisoned and incapacitated by CO. He was fortunate to be alive.

Dr. Frayser was taken by ambulance to a hospital, where the emergency room physician put him on 100 percent oxygen to overcome near-fatal blood levels of carboxyhemoglobin. Another 30 minutes might have been fatal, given the high dose of CO exposure he received. Please read the full FAA article.
The FAA includes the following advice:

"Carbon monoxide poisoning is a safety issue that pilots tend to ignore, even though it is the most common industrial poisoning accident in the United States. When carbon monoxide poisoning occurs, it can have significant and fatal consequences for aircraft occupants."

The NTSB has also published Safety Alerts for avoiding CO poisoning. In SA-069, they cite four different aircraft accidents caused by CO. They make several conclusions, one of which is:

"Install a CO detector and replace the device and its batteries in accordance with manufacturers’ guidelines. Detectors mounted on the instrument panel with aural alerts and a flash notification are more likely to draw your attention and alert you to a potential hazard."

For the full NTSB Safety Alert 069 and all of their recommendations, please follow this link:
NTSB Safety Alert 69 / Pilots: Prevent Carbon Monoxide Poisoning

Clearly, the FAA and NTSB recommend pro-action on avoiding CO poisoning, with good planning including the use of a CO detector combined with a plan for the pilot to follow when CO is detected.

Design factors for an Airborne CO Detector

Before I begin, I will make one observation: many pilots have installed a stick-on CO detector which changes color during CO exposure. I hate them and think they may cause more harm than good by creating a false sense of security. I have flown in aircraft which had them affixed; almost certainly aged out and worthless. They do not flash or make a sound.  They are easy to ignore. Their failure condition (age) is easily overlooked.

The NTSB and FAA's thought processes do not dig deeply into what makes a good CO detector. Missing in their recommendations are qualifications on accuracy, linearity, aging, indications, and so forth.

I propose the following questions, as part of the design process and user selection criteria. I discuss each one in turn, especially as it relates to the design process of my premium CO detector, CO Pro .

a)  Does the sensor within a CO detector degrade over time, and if so, what is some data thereto?
Yes, sensors do degrade. For a good sensor, this degradation can be measured in many years or even, potentially, in decades. (The stick on detectors have a lifespan of 12 months.)  CO sensors are commonly based on electro chemical designs. This means that the CO sensor has chemical elements within it that change an electrical value (for example, extremely minute amounts of electrical current) in response to higher levels of CO. Here is a chart provided by my selected sensor manufacturer which shows real degradation of the sensor over a period of one year.

b)  Are their conditions which would adversely affect the sensor, and if so, what are they?

Yes, all sensors have limiting factors, such as heat or saltwater exposure. For my product, these conditions are well understood, declared and practicable in operation.  Here they are:

• Condensation and Water 
• Salt Water Contamination
• High Temperature Operation (> 70C) for more than 1 month
• Low Humidity Operation (< 15% RH) for more than 3 months
• High Bias voltage
• Highly contaminated air over a prolonged period
• High levels of particles or soot (unless proper filtering is provided)  

This means:

• The product is not designed to be wet or used in rain or in moisture condensing conditions.
• The product is not designed to be exposed to sea spray or any salt water.
• The product is not designed for use anywhere near 70 degrees C (158 F)
• The product is not designed to be used or stored in extremely dry air for more than 3 months
• The bias voltage is a technical design issue. I designed my sensor with a bias voltage of zero volts. This allows the sensor to always be available for use; which allows me to claim the Always On feature of our product.
• The product is not recommended for continuous use in highly contaminated areas.  If you are in bad air, get out, and take the CO Pro with you.
• The product will eventually degrade or fail if exposed to high levels of particles or soot.

c)  Does the CO detector allow in situ recalibration for overall sensor changes (degradation) over years of time?  

It should.  For CO Pro, there is a "linearity" adjustment which is easily reached by the user.  The user may change the linearity setting at any time.  To do this in a meaningful way, the device is placed in a calibrated chamber, the reading on the device is observed, and thereafter, the linearity setting is changed by the user or the test lab.

d)  Does the CO detector allow for immediate recalibration related to zeroing?

It is likely that the CO sensor used within an airborne CO detector will have very minimal localized drift around the zero point. This may be resolved in several ways: by an automatic device calibration, a manual calibration. In CoPro, I offer two solutions: automatic calibration or user zero point calibration on demand, anytime. Using automatic calibration, any drift is detected and zeroed out. Manual zero point calibration is also always available.

In some types of CO detectors, the sensor itself contains a tiny heater. These require a considerable period of time to get to operating temperature. They also use more battery power, but they resolve zeroing issues by performing it automatically after the sensor is heated. This type of detector will be subject to degradation over time.

e)  Does the useful life of the baseline sensor extend beyond 5 years?

This question, along with battery life, are the most common questions from CO detector purchasers. The answer varies by sensor design, of course.

For my product CO Pro, per the base sensor manufacturer, the expected operating life is greater than 5 years. More specifically, once again per the sensor manufacturer:

"The working electrode functions as a catalyst for the electrochemical reaction of the analyte, but is not itself reacted or consumed. Thus, under ideal conditions, the sensor will exhibit a stable response for an indefinite period of time. For typical indoor environmental conditions (23 ± 3 °C, 50 ± 20% RH), a 10 year operating life is expected. Our current long term testing has shown a failure rate of < 1.3 failures per million hours of operation (FPMH). Expressed differently, this illustrates a minimum mean time between failures (MTBF) of >790,000 hours (>90 unit-years!) cumulative operation. For these tests, failure is determined by the UL2034 sensitivity requirements."

f)  Is there a service life history of the part and / or our product which verifies these assertions?

I rely on the assertions of the CO sensor manufacturer which I have chosen. As most products in the aviation market were introduced in the last 5 years, our standing is likely to be similar to other device manufacturers.

g) Does the unit provide a visual and aural alert?  If so, what does the alerts entail?

Every unit on the market provides information via some sort of visual indicator: The black and white LCD screen is the most common.

I chose a full color screen instead. This allows warning information to be shown in several ways:

• Graphing over time
• Current PPM calculation which changes color and value as CO levels rise
• Maximum PPM value which is also color coded
• Arrow Alert points upwards when CO level is rising; it blinks and is color coded with yellow and red 
• Hazard Alert illuminates at critical (100PPM) CO levels; it is presented as a standard red hazard icon.
• Battery Level
• Speaker on / off icon (for muting active aural alarms)
• Screen is dimmable for nighttime use.
• Aural alarm sounds when value is reached (default: 50 PPM)

The screen display is daylight readable, bright and clear.

h)  May the battery be replaced by the user?

If the CO detector uses a fixed (nonrechargeable) battery, it must be replaced as recommended by the manufacturer or when the battery is low, whichever occurs first.

If the CO detector has a rechargeable battery, then it must be recharged. How? For CO Pro, we provide a power only USB port, allowing the CO detector to be recharged.

Every time the power on the unit is turned on, I log a power cycle. This is briefly shown as the unit powers up. Radiant recommends the replacement of the rechargeable battery after 1000 cycles. 

The battery is accessed by removing a sticker and two screws.

i) After power up, how long until the CO detector is ready for use?

Some are nearly instantaneous; others take up to a couple of minutes. In the case of CO Pro, the turn on time is about 10 seconds. Due to the engineering of the unit including the aforementioned Always On circuitry, the unit does not require any heater warm up time. 

j) What about cross sensitivities to other gases?

The CO detector manufacturer should be able to tell you what other gases the detector is sensitive to.

For CO Pro, the cross sensitivities are as follows:

This means that CO Pro reacts with Hydrogen, Carbon Monoxide, and very slightly to Alcohol.

 
k) What about secondary functions of the CO detectors?

Significantly, LightSpeed is selling headsets with built-in CO monitoring, and we are introducing CO Pro with a secondary function as well: G-Meter. The thought process behind this was fairly simple, and was approached from a marketing perspective. Since the CO detector normally is doing very little (reporting continuously @ 0 PPM CO), why not make a useful secondary function? I did this by including the G-Meter. Most aircraft do not have one; most pilots and some passengers want to know how strong the bumps were. The G-Meter is presented in a classic dial format:

The CO levels are shown continuously on the G-Meter screen. Should CO levels rise, CO Pro switches automatically back to the CO graphing screen.

Summary of Use and Design Factors in CO Detectors

I have reviewed the FAA and NTSB guidance and provided links to their documents. The NTSB recommends the use of a CO detector in aircraft.

I have asked these critical questions:

a)  Does the sensor within a CO detector degrade over time, and if so, what is some data thereto?

b)  Are their conditions which would adversely affect the sensor, and if so, what are they?

c)  Does the CO detector allow in situ recalibration for overall sensor changes (degradation) over years of time?  
d)  Does the CO detector allow for immediate recalibration related to zeroing?
e)  Does the useful life of the baseline sensor extend beyond 5 years?

f)  Is there a service life history of the part and / or our product which verifies these assertions?

g) Does the unit provide a visual and aural alert?  If so, what does the alerts entail?

h) May the battery be replaced by the user?

i) After power up, how long until the CO detector is ready for use?

j) What about cross sensitivities to other gases?

k) What about secondary functions of the CO detectors?

And I have provided answers as it relates to any detector, or more specifically the design of CO Pro, a CO detector from Radiant Instruments. 

If you have questions or background material which you believed I've missed, please drop me an email.

I hope you've enjoyed the read.

My new Carbon Monoxide sensor has superb pilot friendly features!

 Hi!

We're announcing our new CO ProTM carbon monoxide sensor. It is designed by a pilot (me!!!) for pilots and passengers and travelers and has features I've always wanted in a Carbon Monoxide detector. 

Startup Screen on CO Pro

Without much of a drumroll, here's a list of features:

• Five year sensor life; possibly extendible as field experience warrants
• Always On sensor -- useful CO baseline Zero reading in about 15 seconds 
• Rechargeable battery operation via USB power port 
• 5 hour life in Bright
• 10+ hours of operation in Dim mode
• Aural Alarm which may be muted (touch the SPEAKER button)
• Zero Recalibration on demand at the touch of a button (touch the CAL button for 3 seconds)
• 0 to 600 PPM range; 50 PPM denoted in yellow and 100 PPM in red
• Arrow Trend provides visual and aural warning when CO starts to rise, long before final value is settled
• Graphing of CO levels over a two minute period; wraps around to show more information
• Hazard Icon illuminates @ 100PPM and higher
• Brilliant daylight readable color display
• Bright mode for daylight and dim mode for nighttime (touch the DIM button for 3 seconds)
• G-Meter as secondary function (touch the NEXT button briefly and unit will switch modes)
• G-Meter has current, max and min digital values
• G-Meter has standard dial indication as well
• G-Meter has 'Ghosting' feature which shows G history
• G-Meter mode also displays digital CO values even while G-Meter is active
• When used in G-Meter mode, will automatically switch back to CO Graphing mode if CO levels start to rise

We also have another CO sensor which is called GEIGER CO.  

In its own right, the older GEIGER CO is a phenomenal product. Here's a photo of the GEIGER CO (orange metal) next to a CO PRO (black nylon with chopped carbon fiber case)

GEIGER CO and the new CO Pro, side by side

I tested GEIGER CO alongside the new CO Pro and uploaded the resulting video to YouTube.

You can see the video here:  https://youtu.be/aJz5FH31_2o

I am getting over a cold as I recorded that.  I hope you like my robust voice. :-)

Here's a look at the screen of CO Pro during a Carbon Monoxide event:

CO Pro screen during operation.  Note Hazard Icon (indicates +100PPM) and Graphing.

  

Here's a little bit of what's happening in this screen.

• The graph shows a wrapped history of what has happened.
• The Hazard Icon is on; it turns on whenever CO PPM > 100 PPM. 
• The current CO reading is 194.
• The max experienced CO was 212.
• The battery icon shows 3 bars.
• The speaker icon is visible. Whenever CO > 50 ppm the speaker alarm turns on.  We can clear it with the SPEAKER button.

Here's the G-Meter screen.

CO Pro screen during operation, in G-Meter mode

• The Needle shows the current G's (about 1.02 as also shown digitally).
• The 'Ghosting' effect shows needle history.
• Also shown are MAX and MIN g values.
• Below the thin line on the digital value list is CO Max and CO current level. Both are updated while using this as a G-Meter.
• If the unit senses a rising CO level, it will automatically switch to CO graphing mode.

The CO Pro can be mounted with the optional Holster. It is designed for a standard 3 1/8" instrument cutout.

CO Pro shown mounted in optional holster

It can also be mounted to any flat surface using the corner holes.  Rivets; screws; Duct Tape (hint, hint).

Please order the CO Pro (or the GEIGER CO) now.

The pricing and availability are as follows:

CO Pro -- $199 intro offer through the end of the month & year (December 2022).

Optional Holster -- $39 intro offer through the end of the month & year (December 2022). I wish I could include this at no charge, but I can't.  We print them on our $20,000 MarkForged 3D printer and it takes more than one hour of print time.  Also, it is printed using nylon / chopped carbon fiber.  It is an exceptionally high quality print.

Aircraft Spruce has ordered CO Pro inventory for stock and is participating in the intro offer.

Links for purchase are here:

Co Pro™ Carbon Monoxide Monitor – Radiant Technology (radiantinstruments.com)

Radiant Technology CO PRO ™ Carbon Monoxide Monitor + Digital G-Meter | Aircraft Spruce

How I ended up in the Emergency Room with a blood clot

I've had growing concerns over my bradycardia, which is simply a slow heart rate. It can produce fainting, and I've never fainted, but I don't want to.  

A few months ago, I asked my family physician to get a little more aggressive in helping me deal with bradycardia.  He made a referral to a heart doc which fit into my medical insurance plan.

And so, I got to wear a heart monitor for 24 hours.  It showed.... pretty much nothing, other than the usual mix of benign contractions common to many people.  For instance, google "Premature Ventricular Contractions".  My heart averaged 49 BPM for the 24 hour period.  Low, but not a problem, according to the heart doc.

He also scheduled me for a treadmill stress test.  I did it, and I thought I was pretty spectacular.  No problems from my side.  

After I'd returned home, I got a call from the nurse. She advised me that the Doc had seen something suspicious -- he wanted me to take the more detailed version of the same treadmill test, this time with nuclear dye in my blood and pre/post cardiac imaging.  OK, I was concerned now.  We scheduled and took the test.

A day later -- the Doc informs me that there is no significant blockage.  My anxiety fades away.

Four days later -- my elbow, close to the catheter injection site for the dye, gets very tender and starts to swell to magnificent proportions.  It hurts. It is tender. It is warm.  Later, I take a pic of the elbow area:

The area of first trouble is obvious.

Two days after that -- with an unchanged elbow problem, I head to Urgent Care. It's Sunday around lunchtime, and the place is very unbusy.  weird....  The receptionist takes my quick info and schedules me for an appointment.  That's why no one is there.  Patients come in to urgent care, get assigned an appointment time, and leave to return at the appointed time.  Kathy and I do the same: we leave, eat lunch, and return.

When we return, the receptionist has us take a seat for a few minutes, and then advises me that I have an outstanding bill with the hospital.  I'm not sure what to do with the information that the institution that is giving me care first reminds me of financial obligations towards them.  That is so TREMENDOUSLY helpful in making me feel calm and collected.

I get into a room, then a PA comes and takes a quick look at the elbow. Without a great deal of consideration of the history of how I got this Big Bulging Elbow, she prescribes an antibiotic and sends me on my way.  My pleas to get alternative theories as to what is happening in my elbow fall on her very tired and deaf ears. 

Within two days, the swelling subsides, so I'm comfortable that the diagnosis was correct.

A week later, I'm still having symptoms.  Weirdly, some of my veins now feel hard and tender as they march up from my elbow towards my wrist.

Three weeks later, I'm still having symptoms.  The area of tenderness has rotated around the area below my wrist.

Five weeks later, I'm still having symptoms. I take a picture of my arm, marking off the progression of swelling and tenderness.  You can see areas one, two and three here:

A map of affected areas on my arm.

Six weeks later, I'm still having symptoms.  In fact, one of the veins crossing my wrist into my hand is now swollen and tender. That would be Area Four of this growing problem. My body starts to have general aches, like a cold.

One morning, I wake up and look at my left hand.  It is very swollen. My frustration of this situation has met a snapping point of sorts.  I take a photo of my two hands, showing the difference, and I write up a brief history and send it to my primary doc along with the photo.  (I do this using the online patient portal.) 

The picture that (maybe) saved my life

Expecting nothing more than an appointment with the doc, instead, my phone rings.  It is the nurse. She tells me:  "Go to the ER. We're sending the same instruction to you via your patient portal." I'm stunned. I ask for some reasoning, but don't get a lot. I read the email from her in my patient portal, and it also says to go get emergency services. ??? It mentions a possible blood infection.

I walk around the corner to Kathy's home office, and tell her that we are heading to the ER.  She is as puzzled as I am; she can hardly believe it.

The experience at the ER takes five hours. 

So I'll cut to the chase: you already know that Emergency Rooms can be a hell hole of frustration, right?

They triage me in and assign me to an ultrasound of the arm.

That turns out to be a spot-on idea: the ultrasound reveals that I have a blood clot in a vein in my left arm. The NP discusses the chronology of events with me. I am once again struggling to understand how I have a blood clot.  What was the sequence of events? How did it start in my elbow and move towards my wrist?  More questions and assumptions than answers. The diagnosis is a Deep Vein Thrombosis in the Upper Extremity (DVT-UE), which is exceedingly rare. It also has a very high mortality rate. (Since I'm alive, diagnosed, and on appropriate medication, I assume I've dodged that bullet.)

Good news:  It's not occluded, or my hand would be the size of an orange.

Even better news:  a $500 per month drug will solve the problem if taken for a minimum of 3 months.

Even better better news:  the first month is free. The second month has a discount coupon.

I am advised to make a follow up appointment with my primary care physician on my ER discharge instructions. It says to see the doc within "1-2 days".  I call my doc's office the next morning:  first available date is 2 weeks away.  I indicate that I'm happy with that, but what about seeing them within 2 days, per the discharge instructions? The scheduler replies: "that's just a suggestion."

Bottom line:  I was trying to solve the bradycardia slow heart rate issues, and I ended up with a blood clot in my arm.  It's kind of like planning to go to the party, and you somehow end up in the sewer, floating downstream.

I'll try and be a little less bitter in my next post.  I'm currently on day six of Xarelto. I will be taking blood thinners for 3 months.

If you enjoyed reading this post, you should also read my prior post on FAA medical issues relating mostly to depression and anxiety. The link is here:

Standard Pilot Blog: Failing the Medical for emotional reasons? I had some anxiety about that too. (jameswiebe.blogspot.com)

Electronic Production Inflation Blues

I took nearly 3 weeks off. The time was spent communing with moose in Wyoming. Yeah, really, ran into 3 of the critters over the course of my camping trip.  One got very close to the blue chair that I was sitting in, and a few moments later I took this pic.

Nice lady, isn't she? She's a pretty big gal, and she's definitely looking at me. Defnitely looking bigger than I remember moose to be.

Which, of course, naturally leads me to my topic of inflation & a small electronic business. (Sorry for the abrupt turn.)

I've seen social media posts talking up a general mistrust in "supply chain issues", especially as it relates to electronics.  Such as electronics for automotive production, or in my case, experimental avionics. Some people mock the reality of these issues.

Here's my reality.

Around two years ago, I started using a very accurate air pressure sensor, as a basis for the air speed sensor within my line of aircraft instrumentation. Drilling down to the exact part in question, it is a Honeywell SSCDRRN100MDAA5.  It accepts a Pitot line (from the ram air) and also a static line (used to establish the differential pressure), thus providing a basis for digitization and eventual display of airspeed in the cockpit of the airplane.

Here is the invoice from two years ago:

And you can see that I paid $31.52 for each sensor.

Here's the invoice from today, as I bought parts to fill orders from customers.

Over the course of 24 months, the price has gone up from $31.52 to $53.79, an increase of 70% on this part. 

Yes, I bought less. And other electronic distributors are posting lower prices than Mouser, from whom I most recently ordered.  But the other distributors have zero stock.

You can see this for yourself by using the global chip finder which is:  FindChip.com, and inserting the part number SSCDRRN100MDAA5 into the search field.  Every part in the distribution system on the planet will show up.  Most distributors have zero stock; the ones that have parts have high prices.  Pick your poison: ship nothing and suffer; or buy parts and kill your margins.

Meanwhile, I have not passed any cost increases on to my channel or distributors. And I'm going to be the bad guy by eventually passing these increases on... except I'm not.  I'm just a small businessman trying to maintain margins, on average, across the board.

Which gets me to the bad news: The promotional prices for Radiant Instruments Gen-2 instruments ends at the end of September. Our older instrument product line will also go up in price starting October 1.  As of this writing, Aircraft Spruce has placed some orders at lower prices, and so they will be receiving some stock of our classic instruments (for instance, Radiant Turn Coordinator) and will be able to honor older pricing while their inventory holds together.  You can always find out what's in stock at Aircraft Spruce by searching Radiant in their website search bar. Most of our product line comes up, and things that are in stock are identified.

Arrgh.

Back to production tasks, now.  I promised Kathy that we would ship some orders tomorrow. 

...Hoping to repair the gross margins next month as prices go up. Hoping people still buy my stuff.

Best Regards,