How to Know when to Change Air-Conditioning Filters

We can actually reduce the running cost of a building by removing the dust from the atmosphere. The furniture, walls and fittings are preserved longer. It also improves the health of the occupants.

Removing dust is usually done by installing filters in the incoming air stream or the circulating air stream. In air-conditioning systems, these filters are installed at the air handling units or AHU's

How do we know when to replace the filters

As more and more dust accumulates at the filters, the differential pressures between the inlet and the outlet will increase. By measuring the differential pressures, we will have a very good indication of how much the filter has been choked by dusts. Persons maintaining the air-conditioning plant should know at what differential a filter should be replaced. Some of the dust particles are so minute, that they cannot be seen by the naked eye. In all appearances, the filter looks as good as new

These are some factors to consider when determining when to change the filter

Mechanical strength of the filter

The final pressure of a filter is usually stated in the product. That is the strength of the filtration medium. However, other factors need to be considered - the strength of the filter walls, frames and holders if not adequately designed can result in the 

In this case, the flow pattern is more important than the particles carried along the air stream. The permissible final pressure loss here will depend on the total pressure and characteristics of the fan and any other control facilities

The filter will affect the air flow as a result of dust accumulation. The filter has to be changed when the velocity of the air in a laminar flow installation cannot be maintained or has fallen below the required specifications