We have many customers ask us this question and, indeed, have visited customers only to see that they have managed to fit their Procart filters back to front. So, this is not a stupid question and you are not alone in being unsure which is the front and which is the back of these concertina filters.
Our standard white, Procart and Procart I filter is fitted with the flatter side facing into your spray booth therefore the deeper folded 'V' section is the back of the filter. The diagram below shows this for you and it also demonstrates how the Procart filter works and how it holds onto the overspray or dust that you produce. The overspray enters the filter through the hole on the front and is drawn into the deep 'V' section. As the air circulates within this area the paint is absorbed by the cardboard and held whilst the air exits the filter via the offset hole on side of the 'V'.
If you have a Procart H, Procart HS or a Procart M2 that are constructed with a fibre layer, then this media should be installed facing the back as it is designed to act as a secondary level of filtration.
Procart H installed in a spray booth