INTRODUCTION TO INDOOR ENVIRONMENTAL QUALITY
- amexcai
- Jul 3, 2024
- 10 min read
Clean air is a primary need, the quality of the air inside homes, offices, schools, public buildings, hospitals or other buildings where a considerable number of people congregate and where they spend a large part of their time, and therefore ende of your life, it is decisive for human well-being and for achieving a healthy lifestyle. The harmful substances emitted by buildings, whether due to construction materials, work equipment or human activities such as the combustion of substances for heating or cooking, lead to a wide range of health problems and can be fatal.
Exposure to aerobic pollutants has caused considerable damage to health worldwide, although it affects all strata, particularly in developing countries. The identification of these contaminants is the first step to specify the necessary actions that must be taken to reduce the health consequences. Indoor environmental quality problems are recognized as important risk factors for human health in countries of all economic levels.
In indoor environmental quality, a pollutant is any substance or manifestation, foreign to the environment in which it is located and that can cause some damage or imbalance, irreversible or not, to the initial environment. Therefore, pollution is the effect (imbalance or damage) caused by the pollutant in the environment that receives it. For contamination to exist, the contaminating substance must be in sufficient concentration to cause an imbalance or damage. The relative quantity can be expressed as the mass of the substance introduced divided by the mass of the receiving medium; This quotient is called concentration.
The type of pollutants are derived from the phenomenon called “Indoor air pollution”, various studies have been developed in which the effects that the identified pollutants cause on the health of the occupants are analyzed in detail.
THE IDENTIFIED CONTAMINANTS ARE:
Carbon monoxide
Substances for wood preservation
Nitrogen oxides
Asbestos and other mineral fibers
Tobacco smoke
Sulfur dioxide
Inert particles (Particulate matter)
Radiations
Microbiological contaminants
Ozone
Pollen and other allergens
Ammonia
Formaldehyde
Carbon Dioxide
Radon and radon derivatives
Hydrogen Sulfide
VOC’s
Introduction to Indoor Environmental Quality.
These contaminants are considered the most frequent and represent the greatest health risks. Note that the previous list does not include pollutants typical of various industrial sectors, such as silica dust, corrosive gases, chlorine, etc., since these are the subject of specific studies in the field of occupational health, however , here we consider them because they are part of certain interior environments, becoming definitive in the health of the occupants and/or users of said environments.
Nor is there any mention of a “pollutant”, whose main effect in terms of health is thermal discomfort, that is, temperature. However, this pollutant, in an extreme case, can represent a severe risk to health when it is a component of the so-called “Heat Stroke”, on the other hand, the presence of a high temperature differential also implies enormous energy expenditure and poses a challenge. the need to recirculate (reuse) indoor air, with the corresponding risks, which means that we must carry out studies to determine whether or not it is advisable to recirculate the air.
Particles, also called 'Particulate matter' i.e. particles in suspension, are a pollutant called physical and are particles, also known as 'total suspended particles' (TSP) are defined as the accumulation of solid or liquid material (dew) in the atmosphere environmental, which are suspended and can be generated from some anthropogenic activity (human process that impacts the environment) or natural, their effect on health is very variable, from temporary symptoms, for example a sick building, to effects severe and degenerative such as asthma.
A very practical way to identify a contaminant in the gas phase is by its smell, which, evidently, is the sensation that results from the reaction of a substance that dissolves in the mucus of the nose, which in some cases, such as that of The petrochemical industry is a very complex mixture of gases, vapors, and very small particles (dust, bacteria, etc.), which can be perceived as extremely unpleasant for most human beings, and in some cases it becomes toxic or corrosive, therefore, it is understandable to think that the way to suppress odors and therefore contaminants in the gas phase, is by eliminating particles and gases or vapors.
The most common way to eliminate particles is through the use of physical filters. Regarding the elimination of contaminants in the gas phase, it is necessary to use their reactive capacity, that is, make them react with “something” to be able to extract them from the air flow, since it is not physically possible because air is also a gas.
There are two ways to produce the reaction between the pollutant and the compound that neutralizes it; The first is the use of chemical filters, which are basically a reactive substance, which can be a salt or activated carbon contained in a container, called a chemical filter, that blocks the passage of air. The second way is to generate compounds that are capable of reacting with the gases contained in the air stream.
The most important aspect is to know which compounds we want to eliminate and their concentration in the air. To know this information, there are two ways: The first is for the personnel involved in the process we want to control to inform us which ones they are. said compounds and their concentrations; and the second is that we carry out a test to determine them.
To eliminate contaminants in the form of gases using reactive compounds, what is done is to introduce these compounds into the air stream (flow), which can be: Ozone, hydrogen peroxide, free radicals, etc., for this it is necessary to first produce them. in sufficient quantity to achieve the desired objective, but in safe concentrations, that is, it is necessary to know the required doses.
Biological contaminants are viable particles, that is, microorganisms, and as particles, the way to extract them from the air stream is using physical or mechanical filters. But that is not all in relation to biological contamination, since it represents a severe risk to health, therefore it is necessary to eliminate the so-called biological load or also known as biological activity. To do this, it is necessary to use some type of element that neutralizes or eliminates viable particles in all their forms: bacteria, viruses, fungi, mold and spores. Said element can be of different types, such as a disinfectant substance, whose most important characteristic is that its principle of action does not induce a mutation in microorganisms and they end up developing resistance to its effect, or a type of energy that is capable of " destroy” microorganisms.
Depending on the type of pollutant, the health effects may be more or less serious. However, there are no harmless contaminants; Any exposure to a polluting agent poses a risk, for example: In general, dust or particulate matter (particles) causes irritation of the respiratory tract and, after repeated exposure, can lead to chronic bronchitis, asthma, etc. Other types of dust (asbestos, silica, etc.) cause specific diseases such as silicosis. There are types of dust that can also be explosive in confined environments (coal, rubber, aluminum). In general terms, the health damage caused by pollutants can be classified as temporary, permanent and fatal.
Temporary damages are those that occur for a short period of time (hours, days), and that remit without specific treatment. They are usually associated with the so-called “Sick Building Syndrome”, when the individual stops exposing themselves to the pollutant or abandons the contaminated site.
The term Sick Building Syndrome (SBS) was coined to describe situations in which the occupants of a building experience health and comfort problems that are related to the time they spend inside the building. but no particular cause can be diagnosed. Conditions may be localized to a specific room or area or may spread throughout the building. In 1984, the World Health Organization reported that up to 30 percent of new and remodeled buildings could be subject to excessive complaints related to indoor environmental quality. Although this condition may be temporary, some buildings have long-term problems. Generally, these problems arise when the building is inadequately maintained or operated with procedures inappropriate for its design.
Permanent damage, health conditions for long periods of time and/or difficult to recover, are those that require specific treatment and in many cases the patient never recovers their health to 100%, they generally develop in work environments, since they are the product of long periods of exposure. Finally, fatal damages, which are those in which the cause of death is directly linked to the contaminant, this does not mean that the death takes place in a short period of time from the exposure, can be of two types:
Occupational or professional, which occurs when exposure to the contaminant is in the work environment and the example may be pneumoconiosis, or some types of lung cancer.
Involuntary, which can also be called Casual or Random, which is when exposure to the contaminant occurs involuntarily or as a consequence of our presence in a certain place, as in the case of a nosocomial infection, exposure to a radioactive source, a accident caused by a concentration of pollutant, etc.
Many of the pollutants found in indoor environments are chemical substances that occur in the form of gases or vapors, some others are identified or defined as “particles”, which may or may not be viable, that is, microorganisms. To know the type of contaminant, sometimes it is enough to know the composition of the material that causes it, the equipment or construction materials of the premises, the processes that take place there, etc. However, sometimes it is necessary to perform analyzes of air samples, which can be chemical, physical, radiological, particle counting and biological.
One of the first aspects to determine is whether the particles are or represent a biological risk (biological load), that is, they contain microorganisms that represent a danger to health. Another very important aspect to evaluate is the size of the particles, because as we know, our body is equipped with natural defenses that in this case are responsible for preventing the entry of a certain size of particles into the respiratory system. These defenses are made up of the hairs. and mucus, however the smallest particles are the most dangerous, since they remain in the air longer and can penetrate through our defenses to the deepest places in the bronchi, and from there develop diseases such as those mentioned in the WHO study.
According to the above, the greatest risk is in dust that cannot be seen with the naked eye.
To establish a clearer and, above all, measurable definition, it is considered that respirable dust, “It is the fraction of dust that, referred to spherical particles of density 1, includes 98% of particles of one micron in diameter and smaller, the 75% of those of 3.5 microns, 50% of those of 5 microns and none of those with a diameter greater than 7 microns.” For this reason, not only the total atmospheric dust must be measured, but specifically the so-called “respirable dust.”
Once the pollutants existing in the interior space have been defined or identified, the next step is to identify the source of the pollution. For obvious reasons we will refer only to the pollutants contained in the air, even though some air pollutants are introduced into the air. interior space from other fluids, such as contaminated water. There are two types of sources; the internal and external lines.
Internal or endogenous are those that are found inside the space, such as in a laboratory, or the emanations from office equipment, furniture, etc. And the external or exogenous ones are those that are located outside the interior space and that are transported inside due to the effect of ventilation or introduction of air. In this classification we must refer to the type of contaminant: biological, physical and chemical.
The type of source of the contamination provides the guideline for the solution.
For endogenous sources and to resolve the issue of contaminants that come from inside the enclosure, it is necessary to resort to the so-called forced or mechanical ventilation, in its very particular variant of extraction, also called Exhaust Ventilation, LEV for its acronym in English. (Local Exhaust Ventilation). The above means that the distribution of the physical elements that make up the interior environment must be analyzed: Furniture, equipment, office areas, process areas, etc.
IT IS IMPORTANT TO CONSIDER:
The location of the contamination source(s)
The quantification of the contaminant mass dumped into the medium, expressed in flow units (lps, ppm, etc.)
The routes and/or trajectories of the staff
The movement of air (windows, ducts, extractors, etc.).
With the aforementioned information properly described in a plan, map or flow-gram, the amount of air that needs to be extracted from the enclosure is determined, and the way in which it should be done. To do so, it is necessary to meet the following objectives:
Help the facility manager select the correct type of ventilation
General Ventilation
Localized Ventilation
Generate a document that clearly expresses ventilation requirements
Establish the relationship between the extraction and the contaminating source
Develop an operation manual for the system, not just the equipment
Develop the system record “book” model
Determine which are valid CAI indicators
In what ranges should you operate?
How will they be measured?
In ASHRAE standard 62.1, different “types of air” are defined based on their quality, and based on this differentiation, criteria are established for their use.
In this same standard (ASHRAE 62.1) you can obtain an accurate guide to determine the ventilation requirements with outside air depending on the type of space, its occupancy and designated area; a small sample is presented below.
Once the volume of air that must be extracted from the room has been determined to prevent the dispersion of contaminants inside, and thus maintain the required air quality, it is necessary to establish the treatment that will be given to the air that will be introduced to replace the one that will be extracted, and that is done depending on its quality. In other words, an important aspect that should not be overlooked is evaluating the quality of the outside air, since it is possible that some contaminants (gases or particles) must be eliminated before introducing it to the room next to be ventilated.
In this way, it is concluded that the quality of outdoor air is an inalienable part of any building and this links us to the next type of source of pollutants, those that are produced inside the premises. Therefore, to achieve and maintain adequate environmental conditions, that is, to have the required air quality, it must undergo different processes before being introduced. These processes consist of: modifying the temperature, modifying the relative humidity and cleaning the air.
Finally, when introducing the air, a good distribution of it throughout the room must be achieved, without forgetting that the purpose of this operation is to remove the contaminants that are produced inside, this process is called distribution or movement. The term used to refer to it is: Air Changes per Hour (CPH) and we must ensure through good design, ducts and diffusion systems that we meet this objective.
With all of the above, we can say that regardless of the use of the facility, it is necessary that the indoor air has the required quality to guarantee that the activities carried out are safe and efficient, with this we will contribute to improving the world we inhabit since we will save energy and provide comfort to users of closed spaces, which will produce pleasant work environments.
The required air quality is that which guarantees that the activities carried out in the premises are adequate so as not to put the operation at risk and do not cause dissatisfaction among users.
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