Key words: Microbial microclimate, microorganisms, extremophile, bacteria, viruses, mites, molds

MICROBIAL MICROCLIMATE

Microbial microclimate is made up of microorganisms - bacteria, viruses and molds occurring in the interior of buildings. A serious problem is especially spores, fungi and pollen particles, which can trigger allergic reactions.

Bacteria are microscopic single-celled microorganisms of various sizes. The average bacterial size is about 0.3 - 2.0 μm. Some aquatic bacteria have a size of several tens to hundreds of micrometers.

Viruses are non-cellular microorganisms of genomic nucleic acid encapsulated by a protein coat, which can only reproduce inside a host cell.

Mites are a number of small arthropods from the class of arachnids whose bodies have merged into a single whole. Many mites are parasitic and dangerous carriers of disease.

Fungi (mold, fibrous microscopic fungi, micromycetes) are multicellular microorganisms. Molds grow in the form of multicellular thread-like structures called hyphae. Fungi that exist as single cells are called yeasts.

According to the method of entry into the interior are three sources of microorganisms:

• Outdoor air as a source of microorganisms
• Air-conditioning equipment of buildings as a source of micro-organisms
• Human as a source of microorganisms

 
The most common, but not the only, source of microorganisms are humans themselves. People spread germs microorganisms in indoor and outdoor air. Microorganisms are then spread to air-conditioning and air-conditioning equipment.

The main carriers of microorganisms are liquid aerosols and solid aerosols (dust). Therefore, it is necessary to prevent the accumulation of dust in enclosed and hard-to-reach air ducts (by means of back flaps, guaranteed overpressure, etc.), as there is a risk of viruses and molds with unlimited life.

An intensive source of microorganisms can be hot-air heating, ventilation and air conditioning systems, filtration equipment, humidifiers and dehumidifiers, air ducts and double ceilings.

Microorganisms that get into the air from clothes, talking, coughing, sneezing remain in a humid air environment for a long time. They associate in the air with fine water droplets that do not sediment. The duration of droplets in the air depends only on their size.

The highest incidence of microorganisms in the indoor environment is in the winter. Most microorganisms for their life and reproduction urgently needs high humidity and temperature. Building and technical objects are not the optimal environment for microbes, yet many families of microbes appear. These microbes need an extraordinary environment for their lives. They are among the so-called extrémophiles.

Selected species of extremophile organisms, including their environmental occurrence:

• Thermophiles - High temperatures
• Psychophiles - Low temperature
• Adidophils - Acidic environment (low pH)
• Alkalophores - Essential environment (high pH)
• Halophyll - High salt concentration
• Barophiles - High pressure
• Oligophils - Low concentration of organic substrate
• Osmophiles - Water unavailability

 
In buildings, psychrophils and alkalophiles, or osmophils and oligophils, are the most common.  Structural elements of houses and flats (wooden beams, masonry, floor coverings, window frames, etc.) can be sources of molds that need to have conditions for their existence and further growth. These are four basic conditions, the so-called moisture requirements, temperature requirements, pH building materials requirements, nutrient requirements.

Mold can be expected wherever there is high humidity. Building structures with high humidity are a breeding ground for mold.  In recent years, there has been a rise in mold incidence in many dwellings. The reason is replacement of windows. Insufficient ventilation (new airtight windows) causes a rise in humidity. Another source of moisture, as shown by the State Health Institute, is also the leakage through the roof or the rise of the groundwater. These defects are not only aesthetic, for most of these fungi are allergic to humans. The influence of oxygen and the influence of solar radiation may vary from species to species.

QUALITY OF MICROBIAL MICROCLIMATE

The quality of the microbial microclimate is evaluated according to the acceptable concentration of microbes - for residential environments is max. 200 to 500 microbes/m³, in the urban environment there are concentrations of up to 1500 microbes/m³. Environmental quality requirements for conventional buildings are met, if bacterial or mold concentration do not exceed of 500 KTJ/m³ of air (colony forming units).

OPTIMIZATION OF MICROBIAL MICROCLIMATE

Optimal microbial climate can be ensured in two basic ways:

• Intervention to the source of microorganisms
• Intervention in the transmission source resource field to the exposed subject

Intervention into the source of microorganisms include, in particular purity skin care, clothing and footwear and isolation of patients. It is recommended to replace the shower chamber in the air conditioning system by a steam humidifier where the humidification is achieved by spraying the water vapor to the heater. It is necessary to drain condensed water vapor. It is better to choose dry methods than dehumidifying equipment than condenser on the radiator. Dryer air filtration methods are better, ie the relative humidity of the air through the filter does not exceed 70%. Elimination of the occurrence of condensation of water vapor on the walls can be done by the addition of thermal insulation, a suitable method of heating, ventilation and dehumidification equipment installations.

Interventions in the field of transmission include the reduction of the spread of microbes in a building by ensuring the purity of the interior, removing unpleasant insects, sufficient fresh air (ventilation), air disinfection by UV irradiation, or by the application of suitable modifying substances in the surface film.