It sounds as if you are experiencing a negative airflow problem. I would recommend that you contact a company such as Martin Engineering, or the manufacturer of your dedusting equipment, for possible solutions.
You can find Martin Engineerings' contact information in the directory of this website.
If you have problems doing so, feel free to contact me by E-mail and I'll get it for you.
10668 Newbury Ave., N.W.,
Uniontown, Ohio 44685 USA
Tel: 001 330 265 5881
FAX: 001 330 494 1704