How To Diagnose And Handle Clogged Fume Hood Filters?

Judgment of Fume hood filter blockage

Observe the ventilation effect

Airflow velocity variation: Under normal circumstances, the fume hood should be capable of maintaining a stable airflow velocity to rapidly expel the harmful gases produced during experiments. When the filter is clogged, the resistance of the airflow passing through the filter increases, which will cause the airflow velocity inside the fume hood to significantly decrease. An anemometer can be used to measure the air flow velocity at the exhaust port or operation port of the fume hood. If the air flow velocity is found to be much lower than the normal value, it may be that the filter is clogged.

Residual odor: If the filter of the fume hood is clogged, harmful gases cannot be filtered and discharged in time and will accumulate inside the fume hood, causing the operator to be able to smell a distinct odor. For instance, during chemical experiments, pungent odors that should have been filtered out, such as sourness and the smell of organic solvents, will be released again.

Check the system pressure

Abnormal pressure gauge reading: The ventilation system of a fume hood is usually equipped with a pressure gauge to monitor the pressure inside the pipeline. When the filter is clogged, the pressure inside the ventilation duct will rise. Observe the reading of the pressure gauge. If the pressure value is found to be significantly higher than the normal range, it indicates that the filter may be clogged.

The operating status of the fan: A clogged filter will increase the load on the fan, causing abnormal operation of the fan. You can observe the operating sound and vibration of the fan. If the fan makes abnormal noises or the vibration intensifies, it may be because the filter is clogged, causing the fan to need more power to maintain ventilation.

View the appearance of the filter

Dust accumulation: Regularly inspect the appearance of the filter. If there is obvious accumulation of dust and debris on the surface of the filter, it indicates that the filter may be clogged. For instance, when a high-efficiency air filter (HEPA) gets clogged, there will be a thick layer of dust on its surface, which affects the filtration effect.

Deformation or damage: A clogged filter may cause uneven internal pressure, leading to deformation or damage of the filter. Check whether the filter is deformed, bulged, cracked or has other conditions. If so, it will not only affect the filtration effect but also may cause the leakage of harmful gases.

Treatment for clogged fume hood filters

Mild blockage treatment

Clean the filter: For some washable filters, such as primary filters, they can be cleaned by using a vacuum cleaner or rinsing with clean water. When using a vacuum cleaner, choose the appropriate suction head to thoroughly remove the dust on the surface of the filter. If rinsing with clean water, be careful not to use too much water flow to avoid damaging the filter. After cleaning, air dry the filter or wipe it dry with a clean cloth, and then reinstall it in the fume hood.

Reverse purging: For some medium-efficiency filters, the reverse purging method can be adopted for cleaning. Use compressed air or a fan to blow in from the air outlet side of the filter in the opposite direction to blow out the dust clogged inside the filter. When performing reverse purging, it is important to control the purging pressure and time to avoid damaging the filter.

Treatment of severe blockage

Replace the filter: When the filter is severely clogged and its filtering performance cannot be restored by cleaning or reverse purging, a new filter needs to be replaced in a timely manner. Select a filter that matches the model and specification of the fume hood to ensure that its filtration efficiency and size meet the requirements.

Replacement operation steps: Before replacing the filter, make sure to turn off the power of the fume hood first to ensure safety. Then, following the user manual of the fume hood, locate the installation position of the filter, unscrew the screws or clips that fix the filter, and carefully remove the clogged filter. When installing a new filter, pay attention to the installation direction of the filter to ensure it is consistent with the ventilation direction of the fume hood. After installation, tighten the screws or clips, turn on the power of the fume hood, and conduct a ventilation test to check if the ventilation effect is normal.

Measures for preventing blockage

Regular maintenance: Develop a regular maintenance plan for the fume hood filter. Based on the usage frequency of the fume hood and environmental conditions, determine the time intervals for cleaning or replacing the filter. For instance, fume hoods used in highly polluted environments may require more frequent maintenance of filters.

Optimize experimental operations: During the experiment, minimize the generation and emission of harmful gases as much as possible. For instance, controlling the usage of reagents and adopting sealed experimental apparatus, etc. This can reduce the load on the filter and extend its service life.