Negative pressure unit for dust control
A popular way to perform passive dust control is using a negative pressure unit. In practice, this is done by compartmentalizing the area where the dust is generated. Partitioning is usually inadequate for dust prevention. Therefore, a required number of negative pressure units are placed in the compartmenting space to make the repair area under-pressurized relative to the surrounding spaces.
From the compartmented and pressurized space, air is removed so that the replacement air flows from the clean space to the dirty space. The contaminated exhaust air is generally directed to the open air through a plastic tube.
The negative pressure devices should be positioned on the different sides of the space to be repaired, so that the largest possible area is within the ventilation area. The negative pressure must be maintained continuously and under all circumstances and monitored by means of gauges. The negative pressure is maintained until the final cleaning to make sure the desired level of purity is achieved.
Dimensioning the negative pressure units or air purifiers
The design of the negative pressure units must take into account the reduction in power when the filter is loaded. Device specific pressure generation and air volume data are used to select the right number of devices and their types.
Visually, negative pressure can be seen from the plastic walls used in the compartment, which are pressed toward the negative pressured space by the airflow. The vacuum should be 5-15 Pa and the air should change 6-10 times per hour. Replacement air is set to be about 20% less than the air removed. Preferably, the replacement air is conveyed outside the building. However, the appropriate temperature of the replacement air must be taken care of.
Too high a negative pressure is harmful. It can break the seals of the compartment walls, the doors do not open and the operation of the ventilation system can be disturbed. Replacement air may enter the working space through, for example, moisture-damaged structures containing microbes.
Negative pressure in dry-mixing
A lot of dangerous building dust is formed in the mixing of the dry matter, and a negative pressure mixing tent is a general way of controlling dust.
The mixing tent works well in passive dust control, as long as the mixing tent is handled carefully, the filters are serviced daily and the negative pressure unit is large enough – in addition, the worker’s must remember to use a respirator, as the tent does not protect them, only the surroundings.
Source extraction is active dust control. It is preventing the spread of dust at the time it is created. Source extraction devices such as CAMU will save your steps as it moves where you work.
Learn more about how to use a mixing tent and a source extraction devices for dust control at a construction site.