Poor quality printouts can really be annoying. Getting a dirty print-out few minutes to a meeting can be more painful as there is no time to call your technician or your service provider. You will probably attend the meeting with poor quality printouts, right? These might be the main causes of dirt on your papers;
You may be getting dirty copies because your slit glass is dirty. When a user does a copy with wet white-out paint on the paper, the glass is smeared with white stuff thus blocking the scanner light from reading. Therefore, Check for white-out remains on the glass and wipe it clean.
Drum unit constitutes of charger part, OPC drum, Cleaning blade and plastic housing. When any of these is damaged, worn-out or malfunctioning expect dirty printouts. This is mostly rectified by replacing the specific part or the whole drum unit.
Development unit is a part within your printing system which is responsible for image development. If this part is defective, dirty copies and poor print outs may manifest in most of your documents. This can be rectified by either replacing the part or getting repair from a qualified technician.
This is the part responsible for fixing the image on the paper. It comprises of press roller, heat roller and a plastic housing. It heats, melts and presses toner on the paper for a permanent image. Dirty copies/printouts may occur when the heat roller is worn-out. Replacing it will solve the problem.
All said, you might be experiencing dirty copies because of using poor quality or non-genuine toner. Many Retailers of toners are selling the worst quality of the products to unsuspecting customers, you may have just bought it. Please consider buying genuine toners from known suppliers to avoid being conned.