Dictionary

The first letters of the name originating from English "Air Change per Hour". It is a general ventilation ratio that determines how many times the air in the entire space is exchanged in one hour, also called air exchange per hour.

The unit is: 1/h.

ADS is the designation for an older series of sensors. It stands for the first letters of the English name Analog and Digital Sensor. We use this designation for the older series of space sensors with a rotary knob for setting the ideal ventilation switching level and for channel sensors measuring CO2, humidity, cigarette smoke, and volatile organic compounds (VOCs).

ASHRAE - a name created from the initial letters of the English words "the American Society of Heating, Refrigerating and Air Conditioning Engineers". It is a non-profit organization of professionals in heating, cooling, and air conditioning that creates and publishes standards in this field. It is an international organization with more than 50,000 members.

CAV – Constant Air Volume comes from English and literally means constant air volume. It is a type of ventilation control where air is supplied at a constant volume with a variable temperature.

From English Cubic Feet per Minute = cubic foot per one minute – flow unit.

It indicates the flow of gas or liquid in cubic feet per one minute. One cubic foot is 28.3 liters, so 1 CFM is a flow of 28.3 liters per minute.

Colorless, toxic gas without odor, primarily produced during incomplete combustion. Exposure to even not very high concentrations can be very dangerous. The source of carbon monoxide is most often incomplete combustion, smoking, and the operation of motor vehicles.

From English words: Demand Control Ventilation. This refers to ventilation systems whose immediate performance is dependent on the current quality of indoor air, determined by air quality sensors. This leads to an increase in indoor comfort and well-being, as well as significant savings in energy and operational costs of buildings.

The designation eCO2 is used for the so-called estimated concentration of CO2 – from the English term estimated CO2, sometimes also referred to as CO2 equivalent. It is thus a certain estimate of the concentration of carbon dioxide made based on the detected concentration of TVOC (Total Volatile Organic Compounds).

This estimate is based on the assumption that the production of TVOC in the breathing process is proportional to the production of CO2. This, of course, applies where the predominant source of air pollution is people. The output of the VOC sensor in eCO2 values ranges from 400 to 2,000 ppm, just like the signal from a standard carbon dioxide sensor.

eCO2 is mainly used for simplifying the setup of the TVOC sensor, as the concentration of CO2 is, unlike VOC, well known.

EPA = the first letters of the English words Environmental Protection Agency. It is an agency of the federal government of the USA, whose mission is to protect human health and the environment.

Colorless gas with a penetrating odor. It is produced during the incomplete combustion of carbon-containing materials. It is found in automobile exhaust gases or, for example, in tobacco smoke. It is also present in the atmosphere, where it is formed by the action of sunlight and oxygen on hydrocarbons contained in the atmosphere. It is often released from building materials such as wood, particleboard, furniture, carpets, cladding materials, etc.

HVAC is an acronym, a word formed from the initial letters of the English words Heating Ventilation Air Conditioning, and refers to the field dealing with heating, ventilation, and air conditioning of indoor spaces.

Refrigerants are certain chemical substances or mixtures of substances that are used as heat transfer media in the cooling circuits of heat pumps, air conditioners, refrigerators, and similar devices, or are used as driving gases. More modern refrigerants are based on fluorinated hydrocarbons (HFCs), which are volatile substances that do not commonly occur in nature.

These refrigerants no longer harm the ozone layer; however, they are classified as very potent greenhouse gases, which is why they are subject to regulatory restrictions in the EU. For example, these are refrigerants labeled R22, R32, R134a, R404A, R407C, R410A.

IAQ – the first letters of the English words Indoor Air Quality – indoor air quality.

LFL from the English term Lower Flammability – the lowest flammable concentration of a given gas under normal conditions. The limit indicates the minimum concentration of the refrigerant at which a flame can propagate through a homogeneous* mixture of refrigerant and air under specified test conditions at 23.0 °C and 101.3 kPa.

At concentrations in the air lower than LFL, this mixture of gases is not sufficiently effective to burn.

It is expressed in % by volume or g/m3.

*homogeneous = the same throughout its entire volume

NDIR comes from the English term Non-Dispersive InfraRed. It is a designation for a method often used for gas analysis, widely used for CO2 detection.

NDIR sensors are based on the principle of absorption of infrared radiation at a specific wavelength by CO2 molecules. In the measuring chamber, there is a source of infrared radiation and a detector. The more CO2 molecules present in the air in the measuring chamber, the less infrared radiation from the source reaches the detector. The signal from the infrared detector is then amplified and converted to CO2 concentration in ppm.

The letters NLII denote the new series of air quality sensors. They are the first letters of the English name New Line II = New Series II.

The first letters of the English words Near Field Communication, that is communication at a short distance – usually up to 10 cm. This communication occurs wirelessly and is used, for example, for contactless payment with a payment card or phone, generally for the transfer of information.

Nitrogen dioxide is an irritating reddish-brown gas with a pungent odor. Essentially, NO₂ is a byproduct of combustion at high temperatures, particularly the burning of fuels such as oil, diesel, gas, and organic materials. NO₂ is primarily emitted by vehicles, power plants, industrial facilities, etc.

Nitrogen dioxide is associated with some respiratory diseases (e.g., acute bronchitis, asthma) and reduced lung capacity. At high concentrations, it causes inflammation of the airways. NO₂ pollution is also linked to diseases such as diabetes, hypertension, stroke, or chronic lung disease.

NO_X are nitrogen oxides and include nitric oxide (NO) and nitrogen dioxide (NO₂).

Ozone (O3) is a gas composed of three oxygen atoms. It is a highly reactive colorless to bluish gas with a pungent odor. Ground-level ozone is very dangerous for our health. Ground-level ozone is formed through chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs). This occurs when pollutants emitted by transportation, power plants, industrial facilities, chemical plants, refineries, and other sources chemically react in the presence of sunlight. Ozone acts as an aggressive and strong oxidizing agent and causes respiratory problems and inflammation of the airways.

PAS comes from the English term – Photo-Acoustic Spectroscopy and thus the photo-acoustic principle of gas detection. It is a method used, for example, for the detection of carbon dioxide in the air. The basis is a mechanically stable measuring chamber, in which the air is excited by pulses of infrared radiation at a precise wavelength (which collides with CO₂ molecules). CO₂ molecules oscillate due to these pulses and generate pressure waves, which are then evaluated by a very sensitive microphone. (See the image below.)

The magnitude of the induced pressure changes depends on the current concentration of CO₂ in the air. Subsequently, the thus induced pressure changes are converted to CO₂ concentration.

PM is the designation composed of the first letters of the English term Particulate Matters and signifies a mixture of solid particles and fine aerosols dispersed in the air. These are then designated with the letters PMX, where x indicates the maximum diameter of the monitored particles in micrometers.

We monitor particles of size 10 µm (micrometers) and less, as they penetrate deeper into the body and the body cannot capture them on the mucous membranes of the respiratory tract or expel them by coughing. In principle, the smaller the diameter, the deeper they penetrate into the body.

Sources of PM

Suspended particles generally arise from the combustion process. Natural sources include wildfires and volcanic activity.

Solid particles

They are usually composed of dust, soot, and smoke. They are generated during the combustion of biomass, released from smoldering fires, from combustion engines, industrial plants, power plants, incinerators, from surface mines, and arise during agricultural activities.

Aerosol

Aerosol consists of various chemicals, which can number in the hundreds depending on current meteorological conditions, atmospheric composition, and prevailing emission sources in the area. We can divide them into primary aerosols, which are released directly into the atmosphere, and secondary aerosols, which are formed based on chemical reactions between sulfur oxides and nitrogen oxides present in the atmosphere in the presence of sunlight and other chemicals in the atmosphere.

Sizes of measured PM

PM10

= suspended particles with a diameter of 10 µm and less.

PM2.5

= suspended particles composed of both solid particles and aerosol (fine droplets of various chemicals) with a size of 2.5 µm and less. It is a typical slightly yellowish smog haze visible in large cities during smog situations.

*Interesting fact: A human hair has an average diameter of 70 µm, so PM2.5 particles are about 30 times smaller.

PM is the designation composed of the first letters of the English term Particulate Matters and signifies a mixture of solid particles and fine aerosols dispersed in the air. These are then designated with the letters PM_X, where x indicates the maximum diameter of the monitored particles in micrometers.

PM_2.5 – airborne particles composed of both solid particles and aerosol (fine droplets of various chemicals) with a size of 2.5 μm (micrometer) and less.

It is a typical slightly yellowish smog haze visible in large cities during smog situations.

• Solid particles are usually composed of dust, soot, and smoke. They are generated during the combustion of biomass, released from smoldering fires, from combustion engines, industrial plants, power plants, incinerators, from surface mines, and are produced during agricultural activities.
• Aerosol consists of various chemicals, which can be up to hundreds of types depending on the current meteorological conditions, the composition of the atmosphere, and the prevailing sources of emissions in the area.

We can divide them into primary aerosols, which are released directly into the atmosphere, and then into secondary aerosols, which are formed based on chemical reactions between sulfur oxides and nitrogen oxides present in the atmosphere in the presence of sunlight and other chemicals in the atmosphere.

The designation "ppm" comes from the English words "Parts Per Million." 1 ppm is therefore one part in a million = 1 millionth.

For example, a concentration of 1,000 ppm CO₂ in the air means that in every million molecules of air, there are 1,000 molecules of CO₂ and 999,000 molecules of other gases. Outdoor air currently contains approximately

420 ppm CO₂.

If there are 999,999 red tulips and 1 white tulip in the picture, then there is exactly 1 ppm of white tulips:

RADON is a colorless, odorless radioactive gas that is produced by the decay of radium (an unstable element in the uranium decay series found in the earth's crust) and is considered a significant carcinogen.

Radon is released from the ground and penetrates indoor spaces through leaks in the building's earth mantle, in the foundation slab, openings between the basement and the ground floor, etc., often through passages into the building such as water pipes, waste, electrical supply, natural gas supply, etc.

What is radon measured in?

The volume activity of radon is expressed in the unit of Becquerel (Bq) per cubic meter Bq/m³.

Where the Becquerel unit serves to assess the intensity of radioactive radiation released during the decay of unstable radioactive elements, such as Radon, when the decay of a radon atom releases energy in the form of radioactive radiation.

One Becquerel thus represents one radioactive decay per second.

Bq/m³

In these units, the volume activity of radioactive decay is expressed per unit of time.

 1 Bq/m3 expresses the volume activity of radon, where one radioactive transformation occurs per second in a volume of 1 cubic meter.

Relative humidity is the ratio between the current amount of water vapor contained in the air and the maximum possible amount of water vapor that the air could hold at a given temperature without condensation occurring. Relative humidity is therefore expressed as a percentage.

Dew point – the dew point temperature is the threshold temperature of the air. If we continue to cool the air below this temperature, condensation of water vapor will begin in the form of droplets or fog. In other words, it is the temperature at which the air is saturated with water vapor to the maximum. It is a state when the relative humidity is 100%. It is expressed in °C.

From the English "Temperature Humidity Index," it is actually a numerical expression of comfort or discomfort depending on the combination of current temperature and humidity. The index is used to assess the quality of the environment for people and animals.

TVOC – comes from the first letters of the English term Total Volatile Organic Compounds, which refers to the total sum, or total of all volatile organic compounds. The term TVOC represents a wide spectrum of different organic substances, often chemically very similar and therefore difficult to distinguish. This was the reason for the creation of several different TVOC standards.

UBA (short for the German Umweltbundesamt) is the German Environment Agency, and its mission is to ensure that people have a healthy environment with clean air and water to the greatest extent possible without pollutants.

VAV – Variable Air Volume comes from English and literally means variable air volume. It is a type of control for ventilation, heating, and air conditioning, where ventilation occurs with a variable amount of air. VAV systems change the airflow while maintaining a constant temperature.

The ventilation rate (VR - Ventilation Rate) is a metric used to express the volume of air inhaled and exhaled per unit of time. It is usually stated in liters per minute and is a key parameter when assessing respiratory function, for example during medical tests or with ventilators. The ventilation rate is often monitored in clinical settings to ensure that the patient receives an adequate amount of oxygen and that their lungs are functioning effectively.

VOC is an acronym, a word composed of the initial letters of the English words "Volatile Organic Compounds," or volatile organic substances.

The area of VOC includes a large number of different volatile organic chemicals including benzene and acetone, which are in a gaseous state at normal room temperatures and are mostly harmful to human health and the surrounding environment. Humans release various types of VOC into the surrounding air through breathing, skin respiration, sweating, etc.

Other sources include, for example: cooking, various technological processes, combustion of natural gas, fumes from paints, varnishes, furniture, floor coverings, carpets, cleaning agents, cosmetics, disinfectants, etc.

VOC substances contribute to the so-called sick building syndrome