Indoor air quality - what are PM 2.5's and are they dangerous to children?
PM 2.5 particles are the smallest particles and are in the air inside and outside of our homes whether we have a stove or not (think the finest of dust particles). It is these particles that are dangerous to health for everybody if prevalent in high enough numbers over long periods of time.
A wood burning stove, correctly working, will not exceed small particle safe-guidelines (I will provide some figures shortly) or come anywhere close. A stove sucks air from the room, drawing particles into the fire and off up the chimney and outside.
The conclusions of a US survey in 2019 by the Journal of Exposure Science and Environmental Epidemiology were that homes without stoves had a Median PM 2.5 of 6.65 µg/m3whilst homes with stoves were a fraction higher at 7.98 µg/m3J. As a comparison outside air in central London averages 18-25 µg/m3.
Just think about that for a minute: a home has a natural and normal amount of 6.65 µg/m3 PM 2.5 particles all of the time, 24 hours a day (in my home it is usually around 7µg/m3). Using a wood stove can increase that a smidgen for the few hours the stove is on (whilst still remaining well within recommended safe guidelines). So "very safe" becomes "still very safe".
With regard to clean air DEFRA states that their cleanest and freshest air classed is anything under 11 µg/m3. The World Health Organisation's advice is not to exceed annual average concentrations of PM 2.5 of 10 µg/m3n. Note that this is an average over a whole year so even if your stove was running 24 hours a day, 365 days a year the average PM 2.5 levels would still be within WHO safe guidelines. For most homes, woodburners are only used for a few hours a day, a few months of the year and PM2.5 additions, caused by a stove, are negligible.
Wood stoves and indoor pollution due to PM 2.5 particles (includes Central London and Delhi outdoor-levels for comparison)
Recent press reports (late Dec 2020) discussed PM 2.5 pollution inside houses. These articles all stemmed from one syndicated article. The article is by Rohit Chakraborty of "The Live Forever Club" (https://liveforever.club/resources/rohit-chakraborty) using a sample of just 19 stove users) and this stated:
"The results showed the burners were usually lit for about four hours at a time... During those four hours, average particle levels rose to between 27 and 195 micrograms per cubic metre of air" (under 35 is low, under 11 is there absolute freshest on the DEFRA scale).
This data differs wildly from the US data and I can state that these outlandish levels are not comparable to levels in my own house or other people I know with wood stoves. Lighting the or refuelling the stove in my house makes almost no difference whatsoever to small particulate levels (open my stove door and air is sucked INTO the stove and off up the chimney - "sucks the slippers off grandma" as the old saying goes).
Cooking causes the meter to go up and this is to be expected: the cooking particles are not funnelled up a chimney. Toast caused the PM 2.5 level to shoot up to 92 and well-done sausages peaked at 218. So are we going to ban sausages? How about toasters?
One thing is worth mentioning. When the level does rise it takes quite a while (an hour or two) to fall, unless multiple windows are opening to allow through-air (so post-sausage cooking you will be breathing in very high levels of PM 2.5 for a few hours).
Recent press good news for a change
21 February 2020
https://www.telegraph.co.uk/women/life/give-wood-burning-stove-just-had-installed/
So much is bad for us in modern life: sugar, wine, time spent online, stress, and in 2019 I’m aiming to cut back on them all. But give up my stove? Not a chance.
28 Dec 2020
https://www.telegraph.co.uk/family/life/sales-log-burners-booming-can-still-eco-friendly/
Sales of log burners are booming – and they can still be eco-friendly
"Whatever the choice of fire, I know that mine has been, hands down, my most satisfying purchase." Jessica Salter