How to clean HVAC filters?

• Engineering department Technician shall confirm from concerned department
• that there is no activity in the area or machine for which filters to be cleaned.
• Operator shall open service door of the AHU/ machine and remove the filter from filter housing.
• Operator Shall put the dirty filters in a Poly bag and take the dirty filter to the filter cleaning area.
• Operator Shall Take out the filter from poly bag, spray the potable water (Pre Cleaning) on filter media from back side and final cleaning with purified water) at a pressure of 1.5 to 2.0 kg/cm² for 4-8 minutes. 
• After rinsing with purified water, engineering operator shall dry the filter with compressed air at NMT 1.5 kg/cm²pressure for 3-5 minutes.
• After removing water with compressed air, engineering operator shall keep the filter on the racks for fully dry.
• Operator Shall check the integrity and any physical damage of clean filter visually in the light.
• If found any damage, then change damage filter with a new filter of similar specifications.
• Operator Shall put the clean filter in a poly bag and transfer to its place for installation.
• Operator Shall clean the filter housing with vacuum cleaner and duster.
• Operator Shall fit the filter in its designated place and ensure that no any gap is left in filter and filter housing.

Frequency for cleaning of HVAC filters shall be: -

Frequency of Cleaning of Filters

• Pre-Filter                               Weekly±2 Days or DP indication
• Pre-Filter                               Weekly±2 Days or DP indication
• Fresh Air filter                       Weekly±2 Days
• Fine Filter                              15 ±2 Days or DP indication
• RLAF Pre filter                      Weekly±2 Days/ DP Alarming or during product change over
• RLAF Fine filter                    15±2 Days or DP Alarming
• Return Riser Filter                 Weekly±2 Days or during product change over
• Frequency of Replacement of Filters Fresh Air Filter After every 2 years ± 15 days
• Pre-filter (5 µ)                        After every 2 years ± 15 days
• Fine filter (3 µ)                      After every 2 years ± 15 days
• HEPA Filter (0.3 µ)               After every 4 years ± 15 days

(Note: - if any filter found damaged it can be replaced immediately)

Repairing and Replacement of HEPA Filters:

• If side leakages are observed between filter and housing, then replace the gasket and seal the gap with silicon sealant. 
• Acceptance Limit: During filter integrity if the downstream leakage exceeds 0.01 % from the gasket, change the gasket. After rectification of the leakage if the leakage does not fall within 0.01 %, replace the HEPA filter with new one.
• If HEPA filter need to replace, switch off the AHU, close the supply damper, close the fresh air damper and open the HEPA filter from filter housing. Clean the housing area and put the new HEPA filter in housing. Fill silicon sealant in the edges and corners of filter housing and terminal box and tight all the bolts. Check the HEPA filter integrity and if the filter passes in integrity, open the supply and fresh air damper. Run the system for at least 30 minutes. Check the particle count in respective area. If particle count of area is under limit of respective class, then hand over the area for Fumigation and Microbial Count Test. Ensure filters are installed in the same place and same AHU after cleaning.
• Inform to user dept. after completion of activity.
• Start the AHU and observe pressure on Magnehelic gauges is within specified ranges.
• Return Riser filters installed in the manufacturing area and LAF/RLAF of warehouse shall be cleaned and maintained by the respective user dept. with appropriate documentation.
• Destruction of Filter
• Put filter in poly bag then shifted to scrap area.