There are three different stages to the LEV test.
Stage 1 – Thorough visual and structural examination.
A visual examination of the system to check that all parts of the system are in good condition and clean. This check can comprise of all, or some, of the following parts.
- An external examination of the entire system for damage and wear of the parts.
- An internal examination of the ductwork.
- Checks on the filter cleaning devices such as dust shakers or reverse air pulse systems to ensure they operate correctly.
- Inspection of the actual air cleaner. For example, damage to the filter fabric can make it ineffective.
- A check on the differential pressure gauges that measure the pressure drop across the filter material.
- Checks on the water flow to wet back booths and wet scrubbers.
- Checks on any alarms that the system may contain.
- An inspection of the fan. Such as whether it is operating in the correct direction, and whether the drive belts are working effectively and if it is vibrating or noisy.
- A check for settled dust around the hood.
Stage 2 – A technical Test of the LEV’s performance.
A check of the technical performance to show if the system still meets with the commissioning data or other sources of relevant information.
- Observations of the process and the hazard source.
- Smoke to examine the airflow into the hood. This can also include the capture distance of capture hoods or air leakage from enclosures.
- Dust lamps used while the process is operating to check for capture of the hazard by capture hoods or leakage from enclosures.
- Measurements of the ventilations’ performance, such as
- Airflow velocity measurements from the hood and ductwork.
- Also, the calculation of the overall flow rate.
- Measurements of the static pressure behind the hood, in the ductwork and across the filter media.
- A check of the makeup air supply to ensure that it is efficient.
- Checks of fan speeds and direction.
- Checks of air cleaner performance for air that the LEV returns to the workplace.
- Simulation of failures to ensure that alarms work correctly.
- Synergy can also measure the levels of discharges to atmosphere through its stack emission monitoring service.
How the technical test is used
After the LEV Tester takes the measurements, they compare the results to the system design criteria. This can be in the commissioning report, the user manual or the requirements of HSG 258. It may then also be possible to make simple alterations to return the ventilation to full working order. An example of this is a system has become out of balance because of the position of its dampers. If the ventilation is not working correctly, then the owner should stop the system until its performance has been corrected.
Stage 3 – A test of the LEV’s effectiveness to control the hazard.
The purpose of the Test is to ensure that the ventilation continues to contribute to the control of exposure. Synergy uses
- the visual and structural examination.
- observations of the process and the way that the operator uses the system.
- the technical measurements.
- including workplace air monitoring to make this assessment.
If the ventilation is able to control the contaminant in all circumstances, then the technician issues a certificate (in a report) to show this.
Synergy marks each of the hoods and test points on a system with a label. Where appropriate, the technician also marks it with the capture distance. The system is also labelled with a certificate to show that it has been checked and to show operators and supervisors when the LEV next needs a test.
If a system fails then Synergy attach a red fail label to show that the ventilation is not working effectively. For example, the reasons a system could fail are:
- if the airflow is insufficient.
- If the hood fails to capture, receive or contain the hazard effectively.
The technician may also use a red label for individual parts of the system that are not working correctly.