It is an air pollutant that contains both solid microparticles and tiny droplets of liquids. Both those and the size of about 10 nm to 2.5 microns. Other designations and names of PM2.5 particles: FSP (fine suspended particles), fine particles, fine particulate matter, fine suspended particles, fine dust.

By source type, PM2.5 particles are divided into:
Artificial (man-made)
The main anthropogenic source of particles is transport. Internal combustion engines and industrial processes with the burning of solid fuels (coal, brown coal, oil), construction, mining, many types of production (especially the production of cement, ceramics, brick, smelting), in cities the source may be road surface erosion and erasing brake pads and tires. Even agriculture is a source of ammonia, from which secondary PM2.5 can form.
Natural (non-anthropogenic)
Sources: soil erosion in arid areas and organic fumes.

Mass concentration of PM2.5 is a key parameter for assessing air quality and its threat to human health. According to the standards of the World Health Organization (WHO), the average annual level of PM2.5 should be no more than 10 μg / m3

In urban air, in principle, there are many different particles: small and large, light and heavy. Only heavy particles "fall" to the ground over time (remember the black snow next to some plant), and light PM2.5 practically do not settle. It is more difficult for small particles to overcome the resistance of the medium and "fall" to the ground. And for the smallest particles, the Brownian motion also exerts resistance.

diameter, um míra vypořádání/ settling rate, m/sek
0,1 8,71-10-7
0,2 2,27-10-6
0,4 6,85-10-6
1,0 3,4910-5
2,0 1,29 10-4
2,5 1,98 10-4
4,0 5.00 10-4
10 3.03-10-3
20 2,20-10-2
40 4,71-10-2
100 2.47-10-1

As can be seen from the table, for PM2.5 particles, the sedimentation rate is 15 times lower than for PM10 and is approximately 0.2 mm / s. This value is compensated even by a slight upward flow of air. And for the so-called PM0.1 ultrafine particles (with a diameter of up to 0.1 μm), the Brownian motion completely prevails over the sedimentation rate. Therefore, this smallest fraction of particles can never settle at all.

PM2.5 particles are also called respirable, respirable fraction. They are so small that they pass through biological barriers in our body: nasal cavity, upper respiratory tract, bronchi. PM2.5 together with air enter directly into the alveoli - vesicles in which gas exchange occurs between the lungs and blood vessels.

see more:

Úroveň CO2 ve vzduchu se měří pomocí jednotky ppm (parts per million).

350 - 450 ppm hodnota totožná s běžným vnějším prostředím
do 1000 ppm doporučená úroveň CO2 ve vnitřních prostorách
1200 až 1500 ppm doporučená MAXIMÁLNÍ úroveň CO2 ve vnitřních prostorách
nad 1500 ppm nastávají příznaky únavy, snižování koncentrace, bolest hlavy
nad 5000 ppm maximální bezpečná koncentrace bez zdravotních rizik
více než 5000 ppm nevolnost a zvýšený tep
více než 15000 ppm dýchací potíže
více než 40000 ppm možná ztráta vědomí

The level of CO2 in the air is measured by ppm (parts per million).

350 - 450 ppm value identical to normal external environment
Up to 1000 ppm recommended CO2 level indoors
1200 to 1500 ppm recommended MAXIMUM CO2 level indoors
Over 1500 ppm there are signs of fatigue, decreased concentration, headache
Above 5000 ppm maximum safe concentration without health risks
More than 5000 ppm nausea and increased heart rate
More than 15000 ppm respiratory problems
More than 40,000 ppm possible loss of consciousness

Perhaps the most frequently exceeded limit value is the 24-hour limit value for suspended PM10 particles, and this is what we will now focus on. Its value is 50 µg / m3 and this limit is considered to be exceeded in more than 35 exceedances per year. We only included stations with min. 90% of the data for each year to make a comparison (if the station does not have 90% of the data and especially if there is no data from the cold season when the limits are more likely to be exceeded, the number would be biased).

The following chart shows the number of exceedances of the limit in the five-year period 2015-2019 at stations in Brno (Kroftova and Soběšice stations are missing for 2019, which are manual and data from them are not available).


Several days ago after the lapse of November environmental lectures in Brno, Czech Republic, record of those lectures now is available in the web to watch. It was a very good lectures, which depict  BRNO and whole Czech Republic air pollution issues, highlight corner questions about the ways how to improve the situation with the air quality, main sources or pollutants and characteristic of the pollutants itself. During the last lecture it was described health problems caused by bad air quality in Czech Repblic.


1. Znečišťující látky a aktuální stav 

1. Přivítání a úvod
Ing. Martin Vaněček
vedoucí odboru životního prostředí
Statutární město Brno

2. Obecný úvod a typy znečišťujících látek
Mgr. Jáchym Brzezina
vedoucí oddělení kvality ovzduší
Český hydrometeorologický ústav Brno

3. Další typy znečišťujících látek
RNDr. Roman Prokeš, Ph.D.
environmentální specialista
RECETOX - Masarykova univerzita

4. Kvalita ovzduší v Brně
Bc. Radek Kronovet
vedoucí referátu ochrany ovzduší
Statutární město Brno

5. Kvalita ovzduší v Jihomoravském kraji
Ing. Tomáš Helán
referent ochrany ovzduší
Krajský úřad Jihomoravského kraje

5. Kvalita ovzduší v České republice a Evropě
Mgr. Jáchym Brzezina
vedoucí oddělení kvality ovzduší
Český hydrometeorologický ústav Brno


If you are not visited this event, but interesting in information about actual air quality in Brno

There are whole presentation and video below:

 (if not avaliable, copy is here: literature/brno_book_2019.pdf )

May be interesting for all BRNO residents.


Three video lectures:



Sincerely yours,