Mains power voltage drop to reduce usage?

Wrong. A key indicator of a badly burning boiler is a headache.

No one cares about bacteria in their central heating primary circuit.

Yes, it does, because of the CO2 and fumes it generates. Even if it is burning correctly.

CO2 at a couple of percent might lead to shortage of breath, and be pretty unpleasant.

For CO the World Health Organisation reckon less than 10ppm long term.

That's 10 parts per million.

But it's your life.

Andy

Unless the level gets high enough to clog things up.

But in the hot water circuit they can be really bad news.

Andy

And in the primary there can be leaks, and happen in your kids bedroom.

I don't have hot water. The shower is electric and so are the washing machine and dishwasher.

I think you'd notice the wet floor.

What makes you think kids are more susceptible?

Yep.

Can high CO2 cause headaches?

Moderate to high levels of carbon dioxide can cause headaches and fatigue, and higher concentrations can produce nausea, dizziness, and vomiting. Loss of consciousness can occur at extremely high concentrations.Apr 1, 2016

Carbon dioxide levels and potential health problems are indicated below:

So I ventilate the room with a fan to outside.

These stoves, if you read the doc linked above, produce CO levels well below the regulated limits by the law. They are labelled CO free. And again, the room is ventilated, and there is a CO2 detector that switches off the stove. Anytime there is CO, there is a lot more of CO2, thus it would trigger the automated shut off safely.

A properly functioning heater doesn’t make CO. The problem comes when they stop working properly. Any appliance that burns hydrocarbons can make CO if the air supply is restricted for any reason, fluff build up in the air inlet.

Tim

CO will produce headache, nausea/vomiting and unconsciousness. Check for the gums, fingernails and corners of eyes going cherry-red: that is caused by carboxyhaemoglobin, in which the haemoglobin in the blood binds preferentially with the CO, instead of the O2 which it is supposed to bind with. Carb-haem is very bright red: much more so than with normal blood, even oxygenated blood straight from the lungs before it has gone to the organs/muscles.

CO2 tends to cause increased respiration because the body's natural reaction is to try to breathe more in the hope of getting enough O2. It's why pure O2 (or O2+N2 with no CO2) in scuba breathing apparatus is a bad thing: the body needs *some* CO2 to stimulate breathing. To much CO2 will lead to unconsciousness but as I understand it, it is not poisonous as such, so a few breaths of normal air is enough to revive a person. CO is much more dangerous than CO2 because removal of CO and breathing of normal O2 will not immediately make the haem give up the CO that is bound to it.

My parents had a scare about 20 years ago. They have a holiday cottage in Yorkshire which is heated partly by a coke/wood stove. Some friends were staying there and one of them woke up in the night feeling dizzy and sick. Luckily she was a nurse and recognised CO poisoning so she got everyone out and opened the windows. The stove flue had got partly blocked by a bird's nest during the months that no-one was lighting fires. My parents felt very guilty and bought several CO detectors. They have also had a cowl fitted which prevents birds getting in and nesting.

But you get the other things first, and do something about it.

Speaking as someone who in the early 1980s became a fully qualified Navy open water deep sea diver and Navy diving medical officer who trained on multiple devices using multiple gas mixtures, CO2 was never part of any of the gas mixtures. I'm talking about normal scuba (compressed air) as well as special diving mixes that combine various ratios of pure oxygen and/or pure nitrogen and/or pure helium. Normal metabolism combined with the physiologic stress of diving plus the work of breathing gases under pressures greater than 1 atmosphere produces all the CO2 the brain needs to stimulate the breathing reflex. Of course, normal scuba uses compressed air which these days typically contains at least 400 ppm of CO2.

I think in submarines the levels are routinely around 4-6%

CO2 simply suffocates you. I've experienced that, briefly.

CO poisons you, but it gives you a headache first.

And its my headache too.

Not in the hot water CIRCUIT, but in the hot water TANK in an indirectly heated system

I think anyone who doesn't fix a primary leak will soon have a depressurised inoperative boiler

More bacteria up your childrens' bottoms....

If the exhaled air is re-breathed (combined with new air from the cylinders) then I can imagine that the amount of CO2 that the body produces is sufficient. The danger comes if all the exhaled air is "lost" and not blended with the tank air: then you need to make sure that the tank air has CO2 in it - which atmospheric air will do but a mixture from oxygen and nitrogen tanks will not.

When I was a kid most everyone had unvented gas heaters in our houses, which burned clean. Fortunately, the houses were usually very leaky. If the CO2 level got high, it would feel stuffy and we'd turn down the heat or lift a window for fresh air.

The hazard would be for the CO2 level to get so high that the gas flames starved and started making CO. That was rare.

The first symptom for CO is usually getting dead.