ACAD Asbestos Industry App: NPU Reduction Calculator
To help our growing membership and the wider Asbestos industry establish a base level IT proficiency, ACAD has launched the ACAD Asbestos Industry app on Android. Here we explore the NPU Reduction Calculator.
As part of the air management for Asbestos removal works, a contracts manager needs to ensure they specify an NPU that is adequate for the specifics of their site.
The ACoP details two minimum requirements for the enclosure ventilation extract rate that must always be met. These are a minimum extract rate of 1,000 Cubic Metres per Hour (CMH) for enclosure less than 120m3 and a minimum Air Changes per Hour (ACH) rate of 8 ACH for all others.
To ensure these minimum values are met, sufficient NPU’s must be used. However, it is important to remember that many things can reduce the performance of an NPU which could mean you do not have adequate air extraction from an enclosure.
In addition to mechanical or electrical issues limiting performance, research published by the HSL in 2013 stated that each linear meter of ducting, for both roving head and exhaust ducting, reduces the CMH rating of the NPU by 1%. In addition, each 90o corner reduces the CMH rating by 2%.
A contract manager should include for any NPU reductions during the planning stage using these reduction figures. These reductions should ideally be applied to the actual NPU that will be used, and to their planned configuration.
Sometimes the actual NPU/roving head/exhaust ducting configuration varies on site. Differences here render the planning calculation incorrect and, in certain circumstances, can mean the ACoP requirements are no longer met.
It is important therefore that where changes are made (or planned) to the NPU/roving head/exhaust ducting configuration then the NPU reduction calculation is revisited.
The ACAD NPU Reduction Calculator removes the errors from this important calculation whilst providing the facility for a permanent record to be made.
A supervisor simply inputs the NPU rating from the latest DOP test certificate, then adds in the lengths and right angles for both roving head and exhaust ducting if present. The calculator automatically changes the actual calculated performance as the figures are added.
To receive a permanent record of this important step, just add a name and email address then click submit to receive your completed report via email. This also includes a time and date stamp confirming exactly when this was undertaken to allow for management oversight and auditing.
Got a smart phone? Get the ACAD Asbestos Industry App…
