Periodic Servicing & Testing

Why Do You Need To DOP Test And Service Your Hazardous Dust Equipment Every 6 Months?

Like all mechanical appliances, wear and tear and damage to "H" class vacuums and Negative Pressure Units (NPU's), necessitates periodic servicing to ensure continuity of performance levels. A "H" Class rating necessitates a more stringent servicing and testing regime to ensure the appliance continues to achieve the performance and safety levels it was manufactured to deliver.

The critical component in achieving 99.995% filtered output in both Vacuums and NPU's is the "H" Class HEPA filter used in these appliances. To meet the required level of specification, these HEPA filters are manufactured to meet very high standards of filtration on an international basis (often 99.999% efficiency). Once installed in an appliance the HEPA filters must then work in conjunction with gaskets and other parts of the appliance in providing the required 99.995% efficiency.

HEPA filters have a finite life and are often subject to damage and wear & tear that can see them fall short of their intended efficiency levels. HEPA filters require correct mounting against gaskets and other machine parts to ensure the appliance as a whole continues to achieve 99.995% efficiency.

H Class appliances can often be compromised in filter efficiency and airflows by:
  • HEPA filters being knocked or gouged when bags are emptied
  • HEPA filters being saturated by solutions such as PVA glues etc (commonly affect airflow and number of air changes per hour within an enclosure)
  • HEPA filters being knocked loose in transit leaving space between the filter and gaskets or being damaged or dislodged when appliances are dropped during use or loading / unloading
  • HEPA filters being installed incorrectly or being omitted completely by untrained personnel
  • HEPA filters becoming clogged, degraded or brittle after repeated use.

Given that harmful asbestos fibres are invisible to the naked eye, visual inspections of appliances whilst helpful, offer no conclusive results about an appliance's continued efficiency levels. A DOP Test is needed to provide an accurate and certified result.

In the case of NPU's, airflow cannot be measured by visual inspection either. A simple airflow test using an anemometer provides a factual measurement that ensures the NPU is flowing the Meters Cubed (or CFM if in imperial) it was manufactured to deliver.

This Meters Cubed (or CFM) is critical in achieving the "air changes per hour" required in an enclosure used for asbestos removal projects. Whilst an NPU can provide 99.995% efficiency, its airflow delivery can still be compromised by a blocked filter