Protections against pollution
The renewal of indoor air allows us to combat internal pollution and Provençal wells contribute by limiting thermal losses. The pollutants evacuated by it have various gaseous forms and can be of human origin, through respiration, such as carbon dioxide, or of natural origin such as radon. Radon is not the only gas that is released from the ground, but it represents a health hazard as it is heavier than air and, above all, a radioactive contaminant. It is naturally present on all continents and regions, mainly those of granitic, volcanic or uranium composition and is mentioned by national authorities (France)[5]. Due to its characteristics, it tends to accumulate in depressions (caves or poorly ventilated places): the risk increases proportionally with its concentration in the breathed air, and it is very carcinogenic, particularly for the lungs. During the design of the well, attention should be paid to the level of permeability of the tube and the joints with respect to this gas to prevent the system from becoming a gas diffuser in the building. An operating well dilutes casual gas infiltrations with fresh air, reducing radon concentrations to an acceptable maximum (with a radioactivity of less than 150 Bq/m³[6]). When used intermittently or after prolonged abandonment, this gas, due to its density, can infiltrate and accumulate in the tube, so it is good practice to initially purge the tube using a valve that releases the contents to the outside without passing through the construction. Another solution may be to reverse the air flows in the house. It is important to note that this occurs naturally if the ventilation of the well is stopped without it being obstructed.
The proximity of a classified industrial zone[7] normally provides for a disaster action plan that includes containment measures such as shutting down ventilation systems. In these cases, ventilation must be able to be stopped quickly, regardless of whether it is natural or mechanical. If the well and its valve are natural, they should be easily clogged; If it is artificial, there must be an accessible switch, fuse or dedicated differential circuit breaker in the electrical panel that allows rapid shutdown of the system. After a chemical industrial disaster, the condition of the well must be carefully checked before commissioning, since the tube may have accumulated heavy toxic gases (for example: dichlorine).
If it is not protected by a grate and filters, the Provençal well can serve as an entrance for animals and particles harmful to the home (rodents, reptiles, insects, pollen...) that can cause illness or discomfort. The filters are installed from the outside to the inside through increasingly finer meshes, which ultimately, like those used against pollen, require greater attention and periodic renewal if the efficiency of the system is to be maintained. By preventing the access of animals and particles, the accumulation of organic matter is limited since the accumulation of feces, food, soil or plant matter for the construction of nests is prevented, and the tube is also prevented from sucking in leaves and dust suspended in the air. Without these, the accumulation over time of a mixture of all the above elements and condensed water could form a substrate for the growth of fungi, mold and/or bacteria. Foul odors following reactivation of a well after prolonged abandonment indicate the presence of decomposing or fermenting matter.
The evacuation of condensate from wells, if drained through sewer pipes, requires the installation of a siphon. The aspiration created by a VMC will not separate the air coming from the well and the stale air from the drain, creating a health risk and bad odors throughout the ventilated building. To maintain its effectiveness and not be a source of contamination, the siphon must be effective and the water must not stagnate, something difficult in practice and which generates the need to monitor the installation.
Good maintenance and prevention are the best way to avoid contamination during the useful life of the installation. Periodic maintenance consists of replacing and/or cleaning the filters to avoid power losses and increased electrical consumption if there are mechanical installations. Prevention refers to examining the condition of the pipe every certain time, three years for example, to know its properties and integrity, especially in areas of pressure loss, such as in the elbows (which should be avoided as much as possible or replaced with open bends).