Asbestos in ventilation ducts is an often overlooked but serious risk in older properties. Asbestos paper, asbestos cloth and asbestos-containing materials were used in the seals, flanges and insulation of ventilation ducts from 1950 until 1980. Sprayed asbestos was a common fire protection and sound insulation in ventilation systems of apartment buildings, public buildings and industrial sites. Sprayed asbestos was already banned in Finland in 1976, but the use of other products continued until 1994.
Why was asbestos used in ventilation
Ventilation ducts are exposed to temperature fluctuations, vibration and humidity, and are subject to strict fire safety requirements. Asbestos met these needs perfectly. The fibers were resistant to high temperatures, dampened sound and sealed the joints airtight. Asbestos paper served as a gasket for the flanges, asbestos fabric protected fire dampers, and sprayed asbestos covered the ducts as a thick layer of insulation.
Typical sites and building types
Asbestos in ventilation ducts occurs in the following locations:
- Apartment buildings centralized exhaust ducts and chimneys
- Public buildings such as ventilation systems in schools, hospitals and agencies
- Industrial halls and ventilation of machine shops
- Business and office buildings central ventilation units
- Through ducts sealings and fire stops
- Ventilation units joint seals and insulated pipes
Especially in 1960 and 1970 apartment buildings and public sector buildings, asbestos-containing components are almost always present if the system has not been renovated.
Sprayed asbestos is particularly dangerous
Sprayed asbestos is loose and soft. In contrast to solid asbestos cement, sprayed asbestos releases fibers from even a light touch. Duct maintenance, inspection or cleaning can be enough to release significant amounts of fibers into the air. Since the ventilation system transports air throughout the building, fibers can quickly spread to all apartments and work spaces. This makes sprayed asbestos in ventilation systems a particularly serious health risk.
ventilation renovation always requires a survey
Ventilation renovation is one of the most common situations in which the risk of asbestos materializes. When the old system is dismantled or the ducts are gutted, seals and insulation will inevitably break. Without survey, it is not possible to know what materials are in the system and how the demolition must be done. Finnish legislation requires an asbestos survey in all demolition and repair work of sites built before 1994, and ventilation renovation is always included in these.
The health risk affects the entire building
A special feature of a ventilation system is that fibers can spread from one leak point to every space that is connected to the system. This has resulted in several large exposure points in schools, offices and apartment buildings. The fibers, when inhaled, cause lung cancer, asbestosis and mesothelioma with a delay of decades. The exposure limits are low, and the minimum safe dose is not known.
This is how you ensure a safe renovation
Before the ventilation renovation, an asbestos survey must be ordered, where samples are taken from seals, insulators and possible sprayed coatings. The survey report guides the selection of the contractor, work methods and scheduling. Asbestos-containing components are always dismantled by an authorized asbestos removal company.
If ventilation renovation is planned in your property and the building is from 1950–1990, order an asbestos survey well in advance of the start of the contract. In this way, you avoid a wide risk of contamination and ensure that the renovation proceeds in accordance with the law.