Source extraction, also called local exhaust ventilation, is the recovery of mortar dust, cutting dust, abrasive dust or other impurities in the construction that occurs near (less than 50 cm) its source of birth. Source extraction devices are cost effective due to the small distance, because the required suction power is small and therefore advantageous to implement. In addition, it is faster and more efficient to collect dust where it is generated before it is released into the environment. Certain facilities and conditions may require the use of source extraction devices, which may be stated by the construction subscriber in the contract.
When using source extraction devices, construction work can prevent the spreading of dust, which is hazardous to health, such as quartz containing dust and other contaminants on the site, and getting into the worker’s breathing zone and the lungs.
Source extraction methods are divided into high and low pressure devices based on the magnitude of their negative pressure.
High pressure source extraction
An effective method for removing dust from, for example, dusting, sawing and grinding work is to use high-pressure, microfibre and HEPA filtering units. These include building vacuum cleaners and central vacuum cleaners. In these devices, the suction line is connected directly to the device. The rule of thumb is that a high-pressure device has a very small suction area and suction is close to the source of dust. In this case, a rapid airflow is created near the processing point, which captures the impurity at its formation. The speed of the airflow is very high in order to recover coarse impurities such as sand and chips. Surveys show that high-pressure source extraction gives about 80–90 % dust recovery.
Low pressure source extraction
At low-pressure source extraction, the air volume is high compared to the high-pressure devices, but the airflow rate is quite low. The equipment’s capture distance is also greater than in high-pressure source extraction. Therefore light airborne particles are recovered from a wide range. The removable source extraction device is placed in the immediate vicinity of a dusty job such as mortar mixing or demolition work.
The Consair CAMU is an example of a source extraction device, i.e. a dust control workstation. Other low-pressure source extraction devices include air purifiers and negative pressure units.
Read more about mixing tents and source extraction devices in dust control.