Wednesday, April 06, 2022

CO2 meters

Remarks on some of the inexpensive CO2 meters I am testing.

Showing CO2 readings from 5 meters in my office. My own breath over a few hours while in a smallish 10x10ft office room with one door open to the rest of the house. Only me in the house (plus a cat).

I had hoped the initial results would be more similar but I do see them converging with time.

[click the picture to enlarge]

The cat and I emit CO2 constantly and we move around the house so the meters fluctuate. There are some tiny seedling plants in the house but probably insignificant CO2 sinks so far so our household CO2 should be reasonably steady. Other gases should not cause deviations. The meters should be specific to CO2 but I've found that the cheaper meters react to other gases.

Please note the range from 623 to 795 (CO2 parts per million), even among these "better" units.

One hour later the average rose to "around 800ppm" where it remained more or less for the day.

800ppm is a NOT a serious level of CO2 in my home but it is worth it to know the relative level.

The meter readings track together but there is a lot of variation. The meters update at different intervals. If I took the same picture 10 times, all would be slightly different. Digital makes one crazy with apparent precision.

I did learn that the CO2 detector inside the meter should be a NDIR (Non Dispersive Infrared) type sensor specifically to be at all useful. The price of NDIR units is typically $50+ (and up to $800 or more).

These are all NDIR meters. The most expensive of mine so far cost about C$200.

In the morning when I first enter the office, the meters will typically show "around 400ppm".  Home heating is on and windows are closed (Canada winter household conditions).

These meters are Li-Ion battery powered and will run for about 6-8 hours or continuously if plugged in via USB. They work great in the car or in your pocket or on the meeting room table.

If I leave a CO2 meter outside (or in my garage) some will read down to 350ppm at times. That is the background CO2 level here which is going up with time but is difficult to measure. Interestingly some of these meters will not read or display below 400ppm at all.

Some NDIR meters will do an automatic baseline (ABC) calibrate function to eliminate the effect of drift. You need to leave them in place for while (days or weeks to stabilize then move them outside for a time occasionally) or follow the hopefully provided calibrate instructions.

Cheaper meters do not use NDIR sensors and are only so-so with CO2. They do not discriminate well other volatile organic compounds (VOC's) like cooking vapours, alcohol or cleaning agents so will show high values sporadically. The cheap meters will drive you crazy with false results. I have about 20 of them.

CO2 meters will also typically show temperature and humidity which are not necessary, related or required for a CO2 measurement. The temperature/humidity are separate inexpensive sensors inside the unit, separate from the CO2 sensor..

More measurement types (3in 1, 5in1 or even 6in1) are not necessarily better than one good CO2 measurement.

Please see my earlier article about the meter at lower right (HT2000).

More soon.

Postscipt Apr 4 2022

Same setup a couple of days later.

I notice that the meters now typically cluster within 75-100 ppm of one another.

It seems that they have become accustomed to the room or each other or perhaps the autocalibrate is having an effect over time.

Thank you for your interest.

George Plhak
Lions Head, Ontario, Canada 

Thursday, September 30, 2021

home electric blog index (new)

Ongoing series since 2014 about managing my home energy.
Click any picture to enlarge. Use BACK to get to this new index.
A work in progress. Comments welcome.

home electric progress
home electric progress 2
home electric progress 3
home electric progress 4
mcmaster study
flexplan/blueline/energycloud/plotwatt update
the base load
my typical electrical day summer
my typical electrical day winter
my typical electrical day winter 2
measurement and control
measurement 2
major appliances
infrared camera
exposing my dishwasher energy hog
more on time of use electricity
more TOU and dishwasher continued
water heater
water heater inhibit to save peak time of use cost
the old water heater
the new water heater
water heater update
heating degree days
heating degree days 2
heat 2
heat 3
heat 4 - the new furnace
chimney cap
superinsulating my refrigerator
insulated refrigerator freezer result negative?
insulated refrigerator freezer 2
EnerGuide refrigerator test specifications
refrigerator 4
refrigerator 5
refrigerator 6
freezer 2
freezer 3
dehumidifier 2
the ontario grid - ieso and sme
efficient workshop lighting 2
clothes dryer heat recovery

Thank you for your interest.
George Plhak
Lions Head, Ontario, Canada

Monday, September 20, 2021

chimney cap

INDEX to the series


Capping my old chimney will hopefully reduce my home energy use.

This chimney has not been required since the old oil burning furnace was removed.

Covered with a tin roof and screen, the old chimney was essentially an open tube from the roof down into my basement.

Although closed off at the bottom, this steel lined pipe was open at the top allowing convective flow from the top of the tube all the way down through the brick chimney core. In other words, some of my expensive heated air was rising out the chimney. Cold air was replacing it by sinking down to the lowest level of the house, right through the center of the house, without much insulation around it.

About stack effect.

The new propane furnace installed three years ago vents through the wall of the basement so this chimney is no longer required. In a major renovation, a chimney like this might be removed entirely from the building and covered over at the roof line but that is not in the plan.

So the next best thing seemed to be cutting the airflow at the top in a permanent waterproof manner. I finally got around to this job three years late. I hate working on my roof.

Above was the top of the chimney showing the 7 inch diameter stainless steel liner and the old chimney cap. That was a pretty large opening into my house!

I used a cutting disk in a grinder to cut through the steel level with the stone and discarded the cap.

On the level surface I laid a bead of mortar then set the patio stone onto the chimney.

Once the mortar had cured, I added a layer of fibre glass tape and roof sealer to the joint.


Thank you for your interest.

George Plhak
Lions Head, Ontario, Canada

INDEX to the series