It depends on where the air intakes are located on your purifier. If the air intakes are located on each side of the unit and the air outtake is located on top of the unit, placing the product against the wall will not affect its function (i.e. AP models, AM190/200/DX55/290/300/DX95), In addition, the air purifier does not produce any heat and does not eject or emit anything that could damage the wall surface. It is completely safe to place the air purifier against the wall.
However, it is not recommended to place the unit against the wall if the air intake is located at the rear of the unit (i.e. AM 90/100/DX5). These models will perform better if NOT placed up against a wall.
If you are unsure where the air intake is located on your model, please click on the Ask a Question button above.