Harmful substances present in our homes

What are the harmful substances that make ventilating our homes essential?:

In any type of building, it is necessary to renew the air, provide clean air and evacuate contaminated air. In poorly ventilated interiors, various types of harmful substances such as carbon dioxide, vapors, fumes, or bad odors accumulate. Additionally, excess water vapor can produce mold and condensation. The main sources of contaminants inside a building are:

1. Increased concentration of carbon dioxide from respiration.
2. Humidity.
3. Machinery and construction materials such as fire retardants, paints, glues, varnishes, and detergents.

The increasing insulation and airtightness in the exterior enclosures of buildings cause these contaminants to accumulate and necessitate planning for an efficient ventilation system that is controlled and continuous. This ventilation cannot be intensive but must be controlled and continuous. Many homes are uninhabited for a large part of the day and are not adequately ventilated. Others remain closed and unoccupied for long periods of time during which ventilation is nonexistent.

Different ventilation systems

Natural ventilation is based on the airflow caused by pressure and temperature gradients, without the need to add mechanical extraction or propulsion means. This model can be efficient in some buildings, depending on their location and bioclimatic variables (temperature variations, frequency and direction of winds, etc.). In hybrid models, there are mechanical extraction means that ensure a negative pressure even when it does not arise from natural gradients. A good design of the system and suitable natural conditions will achieve a minimum operating time for the extractors, contributing to the energy efficiency of the building.

Ventilation in public-use buildings

The need to ventilate buildings properly is more apparent in those intended for non-residential use:

1. Educational buildings
2. Health, care, and geriatric buildings
3. Sport centers
4. Civic and cultural centers
5. Labor and office buildings

In the spaces of these types of buildings, the need for ventilation due to the accumulation of contaminants from their occupants (mainly carbon dioxide) is greater, and it becomes necessary to use high-performance mechanical ventilation systems, such as double flow mechanical ventilation. These systems adapt to the needs and aesthetics of the building, which in many cases has a unique character.

In general, the rate at which carbon dioxide is generated is known and depends on metabolic activity. Since it is the main contaminant in a public-use building, its concentration can be used to assess the indoor air quality. Outdoor air contains around 350 ppm of carbon dioxide, which is considered high air quality. Up to 600 ppm, indoor air quality is considered average, and the maximum value is 1,200 ppm, a level at which discomfort occurs in occupants. To evaluate the need for air renovation, it will be necessary to consider:

1. The expected average occupancy index
2. The duration of user presence
3. The volume of the space
4. The use made of it (metabolic activity of the occupants users)

In a general and simplified way, a renovation index of between 1.5 and 3 volumes/hour is considered minimum or low (moderate indoor air quality), and between 3 and 6 volumes/hour, healthy (medium-high air quality)