Understanding CO₂ air quality better

I have had my new CO₂ meter for a couple of days now, and using it actually requires a bit more understanding than I expected. So here is what I have worked out so far...

First off, what the levels mean!

The tweet I posted listed 1000 ppm as an "acceptable" maximum, and 1400 ppm as "impaired decision making". The 1000 ppm comes from a recommendation of a heating/aircon organisation (ASHRAE), but it seems that was a maximum for comfort and is not in their later specifications at all.

There are other places that talk of 1000 ppm as a target for comfort, and that 600 ppm over the outside level is an "acceptable" maximum (outside typically 400 ppm). I don't understand why the reference to outside matters - one comment is we get acclimatised, but if that is the case then my spending all my time inside (well I used to) would acclimatise me to a much higher level.

Interestingly, the hand-held meter I have has a "calibration zero" feature which involves it being outside for half an hour but what it does is set that as 400 ppm exactly. This makes no sense to me, as calibration needs a known reference and I have measured outside from 430 ppm to 560 ppm at different times and places, so not a reliable reference.

Whilst 1000 ppm may just be for "comfort", I see no reason that I (or my staff) should not be comfortable, and indeed with the prospect of higher levels causing tiredness and impaired judgement, it seems like a perfectly sane target for me to use.

I have obtained a couple of different CO₂ meters that I can leave plugged in for me office (I had a simple temp/humidity one before). It has an interesting view on levels :-

Interestingly it has an automatic baseline calibration that sets 400 ppm as the lowest it sees over the last week. I don't understand why the meter is not accurate rather than relying on measuring my local outside CO₂ levels!

The two meters are pretty consistent, but a bit higher than the hand-held meter - none have been "calibrated" though.

Levels accumulate!

This is what really fooled me. I expected that levels would reach an equilibrium with people breathing and air flow to/from the room quite quickly, so one could measure and see what say "one person working in this 5m x 5m room" gets to. I was wrong.

It my home office today the level started shortly after 9am at 430 ppm, but with just me in here (even coming and going a bit) the level has steadily increased throughout the day reaching 1000 shortly after 2pm. It kept going! It has dips when I was out of office for a walk, and when the outside door was open for a while for a delivery, etc, but it has shown no sign of stopping yet!

This means, for example, when I checked the office and saw 1200, that could have been the result of a reasonably ventilated office with a lot of people and be like that all day, or could just be where it has got to in a poorly ventilated room at that time of day (getting way higher as the day goes on). I'll have to do a trace for the whole day to know.


What I have concluded is my office at home needs some validation. The small vents over the windows (with windows closed) are clearly not enough. My plan is getting some whole day graphs before and after to confirm how well it works, and I'll post more details.

The same is true for my bedroom - not wanting a window open to fight the air-con. I saw that the levels similarly just keep going up when in there awake. Once asleep they do slowly go down, but that was tested with only one person in the room.

I'll post more once I have more data and comparison with the fans installed.

P.S. Nice thing about my man-cave is it has two doors - open both for a minute and you remove all the excess CO₂ and back down below 500 ppm ready to start again.


Air quality and CO₂ levels

I saw an interesting report that a few people in a conference room can quickly result in CO₂ levels such that there is impaired decision making. Wow.

So I thought, I wonder what CO₂ levels I work in normally.

Of course a good start is understanding what CO₂ levels are sensible. Wikipedia has some answers. It seems below 1000 ppm is acceptable, but there safety levels set way higher than that.

I went and got a meter off Amazon (where else!). It seems to be easy to use, and gives two particulate values and a CO₂ value as well as temperature and humidity.

So, first off, my man-cave where I work...

This is a small room, under 5m x 5m, with windows (that I keep closed), two doors (also closed most of the time) and no air vents as such. It has air-con which seems to filter quite well, so the day starts with this - very low particulates and sensible CO₂ well under 1000 ppm. It is only myself in the room normally though.

Once I am in here a while, CO₂ gets to over 900, but it depends what I am doing.

I have a treadmill - if I use that then the CO₂ gets over 1000 in a few minutes.

So maybe I don't need extra ventilation in here - if I open a window when using treadmill perhaps. This time of year a window is not problem but in summer or winter it is not ideal, obviously.

For reference, outside this morning varied between 520 to 560 as I walked through town to Tesco for my Costa breakfast. At Costa it was 700 ppm, and particulate levels of 3. Impressive.

Where next - well, my bedroom. I have air-conditioning in there as well, and as such do not normally have a window open. The bathroom has a window slightly open but the door to bedroom is normally closed. I was quite surprised that during the night the levels were over 1300. I suspect I do need some ventilation! I tried a window but it is behind curtains and did not result in much in the way of extra air circulation or a noticeable drop in CO₂!

I also checked the office, which was around 1200. They have a fan but normally off, so I think we can improve working conditions there. I also wonder what a plant or two would do.

Do I really need to do anything? I am thinking a bit more ventilation perhaps in some cases, maybe. In practice, I am planning to install some almost silent low power alternating external air vent/fans with heat exchangers. I'll report back on how well they work in due course.

Assuming I improve the CO₂ levels I won't be able to say if that makes any difference as no real objective way to tell without huge biases creeping in, I don't think.

However, for one final bit of fun - I went in to the kitchen while there was much cooking (so much that shortly afterwards the smoke alarm went off), even with a couple of windows open...

That was impressive - particulate meters literally off the scale (100 is a level that is bad), and CO₂ at silly levels.

If you can't stand the heat, etc, etc...

And yes, I do like my gadgets.


Serious WiFi case study (a house in Wales)

Two of my staff work from their home in Wales some of the time. Working for an ISP you expect that they have good Internet, and perhaps even good WiFi. Well, they have good Internet with our standard dual bonded FTTC offering, but WiFi posed more of a challenge.

The problem is the house! Whilst old buildings with thick walls are not an issue unique to Wales, they are a problem for WiFi. The outside walls are around a metre thick, and the middle of the house has huge fire places and chimney breast making an even thicker wall. Whilst the basic layout is two rooms per floor (one front, one back), it has three stories and high ceilings.

What this means is one WiFi access point in the front room does not working the back (kitchen). Similarly WiFi on the ground floor struggles on the 2nd floor, if at all. Basically, there is no one place to put a WiFi access point (AP) that will work sensibly for the whole house, or even most of it.

This is a big problem for the traditional arrangement of ISP provided combined router and WiFi AP. Even solutions using WiFi repeaters would struggle, so the best bet is to have multiple wired in APs.

The solution, for some time, was to have several Apple Airport Express APs, around 4 of them. This is very much "on the cheap". For some reason this was not a good solution. Much of the house was not well covered, and even in the same room as an AP a speed test would rarely show more than 1Mb/s and usually the WiFi was unusable - so much so that they took to turning off WiFi on phones and tablets and using mobile data instead, in there own house!

We recently added a new package to our order forms at A&A, a "Serious WiFi" package which includes two WiFi-5 APs, a PoE switch and selection of cables and couplers. The idea is that this gives you the kit to deploy two WiFi APs in such a premises. It is far from cheap.

They finally asked me to come and sort the WiFi, and I thought this was a great chance to test this new "package" which we have started selling in a typical situation. I took the two APs, a PoE switch, and cables. The APs are Aruba IAP-305s which are "WiFi-5" (802.11ac).

The first step was to work out where to put the APs for good coverage. This was a combination of looking at the rooms and the thick walls, and also considering where the mobile devices will most commonly be used. We decided high on the wall on the ground floor at the front facing in to the house, and high on the wall in a back room, on the 1st floor facing in to the house. There are a number of other places we could have set up the APs I am sure.

We unplugged the old APs, as the new ones do a frequency scan to decide on best channels anyway, and we used a double sided sticky pad to stick the new APs to the walls in the selected locations with a loose trailing network lead. This allowed us to test the positioning easily.

We looked at mobile signal strength and speed tests in each room, the results were good. Having decided on the position, this meant a masonry drill to fix the access points properly and cable clip the cable in place. Yes, I am not a decorator, I was only there to "make it work" - there are plans for some white trunking in the near future I gather :-)

We were quite pleased that the solution worked and did not need a third access point, which was always a possibility.

Once done, more testing, and they are over the moon with the result. Phones can seamlessly roam between the two access points. And the speed tests are somewhat better than the 1Mb/s they could manage before.
To be honest I was surprised how much difference this has made. The Apple Airports may be a bit dated, but they should basically work. Obviously the new access points have 2.4GHz, and 5GHz, and multiple radios and antenna, and newer (faster protocols), so this clearly makes a difference.

It does rather prove the worth of the new "Serious WiFi" package though, and I am pleased with the result. Expensive, but compared to "unusable" WiFi before, I suspect it was worth it - and would be well worth it for a business premises.

P.S. We had a bit of fun as well...


Daikin Air-con WiFi control

One of my air-con units was sufficiently ill that we gave up and changed it, and now I have a nice new Daikin one with WiFi control via a phone App.

The WiFi sticker that came with it had a QR code which was oddly not the WiFi login, even though iPhones understand such things, but I got it on to my WiFi (only 2.4GHz by the look of it) and all working with the app on the phone - nice.

What is nicer is poking it using curl. It has a noddy TCP stack and http interface (not https) which makes it very easy to script stuff. Several people have done this, but I have not found quite what I was looking for, so some poking around.

So, here goes, what I have found so far (subject to updates).

Sensor info

A simple get of /aircon/get_sensor_info gets :-


Which is nice as it has room temp and humidity and external temp to 0.1C precision.
  • ret: A return status, with OK being good, it seems
  • htemp: Inside temp in C
  • hhum: Inside humidity, I assume in %
  • otemp: outside temp in 
  • err: I assume an error setting
  • cmpfreq: I am guessing compressor or fan frequency
  • mompow: Not sure, was 1 when idle and when heating, 2 now we are cooling

Control info

This is where it gets useful, a simple get of /aircon/get_control_info gives


What I have worked out so far :- 
  • pow: Power 1=on 0=off
  • mode: 1=auto, 2=dry, 3=cool, 4=heat, 5=?, 6=fan, 7=auto
  • adv: blank normal, 2=powerful, 13=streamer, 2/13=both
  • stemp: Set temperature
  • shum: Set humidity
  • dt1/2/3/4/5/7: Target temp for each mode
  • dh1/2/3/4/5/7/h: Target humidity for each mode (and h?)
  • alert: ?
  • f_rate: Fan rate A=Auto, B=Quiet, 3 to 7=speeds, 
  • f_dir: Fan direction 0=fixed, 1=vertical, 2=horizontal, 3=both
  • dfr1/2/3/4/5/7/h: Per mode something, not sure
  • dfd1/2/3/4/5/7/h: Per mode something, not sure
  • dmnd_run: Not sure
  • en_demand: Not sure
  • b_setting: Not sure

Control setting

Setting is a simple get /aircon/set_control_info?pow=1&mode=4&stemp=29&shum=0&f_rate=A which just responds with ret and adv.
The settings are as above.

So a simple cron to turn off at 06:35 is :-

35 6 * * * curl --silent 'http://x.x.x.x/aircon/set_control_info?pow=0&mode=7&stemp=21&shum=0&f_rate=B' | grep -v OK


Bleeding time and motion

I have a blood test every year, sometimes more often, and that means going to Heatherwood phlebotomy clinic.

They open at 08:30, and at that point there are typically 30 or more people waiting already (which is about capacity for the waiting room). They have numbered cards you take, and they call a number. If you are lucky then there are two of them taking blood.

First off, they really should have a second set of cards (maybe just for the first hour of the day), perhaps in red or something, for fasting blood tests. I was feeling hypo as it was, but had to wait over an hour to be seen. Luckily my test was not a fasting one, but had it been I could well have been collapsing. Normally a fasting test is not a problem for someone, but I have daily insulin, and that can mean some times I have to eat - such as when I have not eaten for 12 to 14 hours for a fasting test. Even though, in my case, it would have put people ahead of me in the queue - a priority queue for fasting would make sense. The blood test form says if fasting or not, so not like people could game the system and take the wrong card.

They are pretty efficient, check your name and DoB, strap arm, clean, find vein, take blood, tape dressing over it, and then spend about 50% of the overall time, or more, writing your name, and details (about 4 lines of text) on each of the blood sample containers (in my case, two).

It strikes me that the system could be massively better with a simple barcode readers and label printer. Even with nothing needing to be on-line, just a QR code on the blood form the doctor sends that when read provides the lines of text to print on the sample label, just that. Such a device would not be expensive (well, not compared to staff time over its operational life) and could mean processing at roughly twice the rate, by my estimate. A simple fall back to writing means not building in a dependancy on technology.

Of course the printed label could also have a QR code which probably then saves time when the samples are processed later, as well as reducing transcription errors.

Don't the NHS have people whose job it is to think of things like this?

P.S. I am surprised someone does not make a small label printer with QR reader that literally just prints the QR label content on a label on each scan. Must have loads of applications just like this!


Over kill?

A friend of mind dropped dead of a heart attach recently, and he was a year younger than me. He was at home, but so easily could have been at work.

It makes you think.

Well, more, it makes you shit scared!

As usual one's assessment of risk is skewed by the most recent experience.

Even so, I do think that the potential life saving benefit of a defibrillator way out weights the cost. More to the point, I can afford the cost. I can't afford to drop dead (IMHO).

We took advice from Red Cross, and we now have one at the office, and I have one at home too. I am surprised more offices do not have one. Our first aiders at work are trained on it as well (thanks to Red Cross), but it is pretty idiot proof.

I hope we never have to use it, either of them.

P.S. From the comments, one thing is getting one that can go outside, and so be accessible to others (e.g. others in my road) if needed. The ones we have are not for outside installation, sorry, but certainly something to consider if you are getting one installed.


Fun game!

I am getting used to the glucose monitor now, and starting to get the hang of keeping things in check a bit more.

What is driving me somewhat mad is how things can be unexpectedly inconsistent. Some nights I can be bang on normal (in the green band) all night; others droppings really low, so much so I wake up feeling ill and even have to have something to eat; but another night gradually going from too high at midnight to too low at 6am as a nice gradual drop. This is all on exactly the same insulin dosage.

Some foods have massively more impact on blood sugar than others, and the clues are on the packaging, obviously. The main peak today was eating 3 jaffa cakes, that was all, just 3.

I have pretty much decided that even if we drive to the restaurant in Bracknell, I need to make the effort to walk back afterwards even if a couple of miles, as that really does knock down my blood sugar nicely.

Though today I have had a couple of lows that I would also like to avoid.

P.S. Yes, I know crisps and jaffa cakes are a bad idea, you don't need to tell me :-)

P.P.S. Yes, it did go up a bit after that, but clearly walking made a dent!


My first Borg implant

Actually, just a Freestyle Libre glucose sensor!

As you will know I am diabetic, but I am reasonably lucky at this point that whilst I don't make enough insulin, I only have to have one long term injection a day. This is, in some ways, a mixed blessing, but I would rather not have an injection with every meal.

When I have a good routine I don't have to check my glucose levels, but I am losing weight (lost 19kg so far) and this is causing a bit of fun and games. I have been lowering my carbohydrate intake and my insulin but I do need to keep things in balance. On top of all of that, exercising is helping and means I am lowering my insulin even more to avoid hypos (low blood sugar) all the time. I was managing to have high glucose and low glucose, both of which are a problem. I was getting fed up pricking my finger to be honest.

So I got a Freestyle Libre glucose monitor. It monitors interstitial glucose levels so apparently has a lag of 10-15 minutes compared to blood sugar glucose, but it is monitoring all the time, and allows me to see how my glucose levels change during the day. It is easy to just scan from my phone by holding it to my arm. It has a memory of 8 hours (I am surprised not longer) so you need to scan at most every 8 hours to not have a gap in the readings, but that is not really an issue.

I am not really the typical user for these. They are also not cheap (over £60 for a sensor that lasts 14 days). Normally these would be used by people that need insulin with every meal. In my case I am trying to make sure my insulin levels are right for a daily dose, but also trying to work out when, and how much, exercise works well to keep my glucose levels in check. Also working out if, and when, and how much Gliclazide I need to take. Having this near instant feedback from the sensor, and the graphs, is ideal. Hopefully I will not need to keep using them as I get in to a more sensible routine.

Basically, at this point, I need to go for a walk after each meal. Doing that, and taking a tablet with my main meal, should keep my glucose sensible all day. But it is a learning exercise for me, and I have only been using this for a few days. I managed to have a level of 12 mmol/l for 9 hours after having a pizza and not going for a walk, but at least I know without having to prick my finger.

I thought it would be uncomfortable to be honest, but not had any trouble sleeping on it. I did catch my arm on a door frame at one point, but otherwise it seems pretty easy to cope with. It is waterproof. I am not sure how easy it will be to get off at the end of the 14 days, I'll see.

Losing weight is good, but definitely causing changes, not just with diabetes. I have actually had to stop taking blood pressure tablets! You do have to be careful changing things like this (and I would suggest asking your doctor/nurse). I reduced dosage slowly and monitored blood pressure carefully - but basically I was getting dizzy when I stood up. Blood pressure of 100 over 60 is a tad low. I now have sensible blood pressure with no medication, which is a side effect I did not expect!

I also did not realise that there seems to be a big market for stickers people put on the sensor! Crazy.


Outside WiFi

Whilst we have excellent WiFi in the house, due to three access points, the garden was not as well covered. A brick wall and conservatory in the way, etc. The WiFi was OK in the garden but I thought I should really try out an actual proper outdoor WiFi access point.

I now have one of these, an Aruba AP-375, and yes, they do cost over £1,000, which is silly, I agree. But it works with the WiFi we have (all one controller), and is clearly robust and weather proof.

We now have excellent WiFi in our garden, and the gardens of several neighbours!

The garden really is not big enough to justify the cost, and if it was not more of an experiment to see how well it works, I doubt I would have got it.

As with the others it is run of PoE, so a simple network cable in to the loft to a PoE switch. I got proper external grade cat5e cable - from Amazon (here).

With solid core network cable you have to get the right plugs that work with solid cable. I actually got some cat6 plugs for solid cable from Amazon (here) which "just work".

I had to also order the wall bracket. Do not be fooled by pictures in the Internet, there is an "H" and "V" version for the surface on to which it is mounted being horizontal or vertical. There are sites selling one with a picture of the other! I fitted with some wall anchors, which, you guessed it, I got from Amazon (here) and drill bit (here).

I walked around the block, and even found a spot on the main road where our WiFi is just visible (through a few houses /gardens). It goes quite a way in open air from high up.

Walking around, it is amazing how many WiFi signals you see. It was nice to see, amongst the VM and BT names, at least one aa.net.uk signal from someone in the next street :-)

Obviously, where these access points make more sense is when you do have a large open space, not just a simple residential garden like mine. We have done WiFi at a beer festival a few times, and if we do that again I can see us putting a few of these in.

When is an email address not an email address?

I just saw an interesting tweet...
This case hinges on what is an email address. The key issue was that someone mistyped their email address on a form, leaving out a dot in the local part and hence did not get an email that was sent. The email did not bounce (which is not that uncommon), so the sender has no way to know the email address was not right.

The judgement is odd to me, it is that it is not in fact an email address if it is not valid. i.e.
I have come to the view that the expression “an email address” means an actual email address and not, as here, an address that has never been set up or registered to any user or users.
So, to be an email address, it has to be set up or registered to a user, whatever that means!

This raises all sorts of questions. What does set up, or registered even mean even? Who has the authority to say if an email address is registered to someone - where is this register kept? What if the email is registered to someone else, i.e. it is not the email address that was intended?

This does, however, raise a huge issue with both judgements like this and legislation like the PECR (The Privacy and Electronic Communications (EC Directive) Regulations 2003). In both cases there is a big issue which seems to have been missed - how does someone determine what they have? How does one actually apply the law/ruling in practice?

In this judgement, how does the sender know if the email address is an email address where the test is whether it is set up, or registered to any user (not even to the intended user). There is no test for that, and no way for the sender to know. They cannot rely on "does the email bounce?" as in this case the email did not, and that was not good enough.

In the PECR there is a test of whether the email address is for an individual subscriber. This too is defined, but it depends on the way the subscriber contracts for the communication service. This is something that the sender has no way to tell, but it changes whether they can send an email without being in breach of the regulations. Essentially the PECR only works if the sender has to assume every possible email address may be of an individual, so is not valid for unsolicited marketing. They have no way to know, meaning ALL emails are in scope and should not be sent (if unsolicited marketing emails). If that was the intention of the law, then why not say that - why create the illusion in the law that sending to commercial subscribers is OK when there is no test a sender can apply in order to comply. Either that of the sender has a defence that they could not know, and so the law is effectively useless. Basically the law is bad law as those that need to follow it have no way to reliably do so.

In this judgement there is a similar issue - the party sending the email needs to know they have an email address or not as it changes what they do and what timescales things have. They have no test they can apply to determine if what looks like an email address is in fact an email address based on this judgement.

Indeed, as warned in the case, the intended recipient of the email can game the system by providing an email they know to be invalid but which does not bounce.

You also have the question of when the email is valid. Is it set up, or registered to a user when supplied, or when the email was sent? Anyone with a domain can decide if and when an email is valid on a whim as they require.

And then there are wildcard domains, which some people have, and emails using wildcards and pattern matches. None of these (as complete email addresses) are registered to a user so does that mean all such email addresses are now invalid, and not an email address under law?


After a bit more discussion, I still feel quite strongly this is just wrong.  The wording is :-
(3)  An early conciliation certificate will be deemed received—
(a)  if sent by email, on the day it is sent; or
To me, this makes it pretty clear that the sender has done their job if they send an email (to the address notified to them). This is pretty common wording for email and post, and it means that if the person providing the address makes a mistake, then that is their problem. The sender is expected to send to the address notified - there is not any more you can expect from them, and it is not their fault if the address turns out to be wrongly provided to them, and also not their fault if the delivery system (post, or email) does not get it to the recipient.

The wording could have been something that requires the recipient to have actually received the notice/certificate. I have seen things like that. That would put the onus on the sender to somehow check the recipient has got it, and make the sender responsible for correct addressing and delivery. But that is not the wording in this case. To me, this means a typo is the problem of the person that makes the typo.

The ruling could have said a typo is the problem of the person making the typo, with possible exception that something that is obviously not an email address should be spotted by the sender (i.e. just has to have the appearance of an email address, or meet the internet standards). The ruling could have said this is all down to communicating, and the email has to actually be the correct one for the recipient, and if the email does not get to them, it is not "deemed received".

To me, the whole point of "deeming" it received is because actual receipt is not the senders problem. If the law as that it actually has to be received, by the right person, it would not need a clause on "deeming" it so.

The actual ruling is in the middle. It says that it is not "an email address" even if it "looks like one" if not "set up" or "registered to a user". So a typo is the problem of the person making the typo if and only if their typo ends up being a valid email address. But if their typo makes an email that is not a valid email address it is the problem of the sender (who has no way to tell there was a typo), even if the mistyped email has a valid domain with MX record and email correctly goes to that server.

Surely the judge should have clearly decided - "whose responsibility is it if a typo is made?" Having decided that, one way or the other, he could make a ruling on whether this is an email address or not. This ruling does not actually answer that.

This comment muddies the water even more :-
Since the object of the Form is to enable communication, the intention must have been to solicit an email address that could be used to send the certificate. If so the phrase must mean an actual email address.  That is what the request on the form sought. I find it difficult to accept that Parliament intended the words “an email address” to include invalid addresses that could not be recognised as an email address by a server and forwarded.
But the email address was one that could be "recognised and forwarded" as the domain part was not mistyped, so the mail could be sent to the correct MX record. This is the same as sending a letter to a postal address. What happens then is down to name or department written on the letter, but it has been delivered to the "address" by the postal service.