I work near a fume vent. what should i do to prevent myself?

Avoidance is best: Avoidance is the best. If this is not possible knowledge of the fumes and their effects will dictate what you should do to protect yourself. Find out what is coming out of the vent and google their effects on the human body. Your work should have msds sheets for all chemical exposures that will help to direct you as well. Check with your safety officer.

Fan: You may reduce your exposure by using a fan to divert the fumes away from you. If you are concerned you may seek assistance from the office of Occupational Health and Safety Administration (OSHA). Wish you good health.

Fumes for what ?: You get the most from this site when you provide detailed background information about your health issue before asking your question. The type of fumes to which you are exposed, the distance from the vent, the fume abatement (protective gear) you wear if any, etc. are all relevant to providing a response. OSHA regulations likely exist for any such exposure if worrisome.