How to Replace the Filter of a Diffuser

Sometimes it is necessary to install an air filter behind a louver, a grille, a diffuser or an air inlet. This is very common in commercial buildings.

Ventilation louvers are usually clipped in place or secured by screws. If no screw is visible, the grille is probably secured with clips.

If this is the case, pull lightly on the grille and the retaining clips will release, giving you access to the ventilation duct.

Measure the dimensions of the duct or the available space. Our Air-T-Rex filters fit most ducts and are very popular for this application. If enough space is available, you can also install a MervPlus filter of 1" or 2" thickness for more filtering power.

How to measure a filter

If you already have a filter, you only have to take its dimensions.

IMPORTANT: Stock filters are usually identified by their nominal dimensions. In fact, the real physical dimensions of filters are about ¼" less than the advertised nominal dimensions. Please take this into account when ordering. In the case of filter thickness, the nominal dimension is the same as the real dimension.

How to install the new filter

Some pleated filters have an arrow indicating the air flow direction. Place the filter in accordance with the arrow.

Attention: Check for air leaks

Pay special attention to the airtight seal around the perimeter of the filter.

An air filter is useful to the same extent as it is airtight around the perimeter. Air always follows the least resistive path. If the filter can move in its casing, air will pass around it. Take care to secure the filter against its frame.