You may very well have a legal cause of action agaist the landlord and/or managing agent and should consult with a personal injury attorney to discuss the matter--many attorneys, by the way, will provide a free initial consultation to evaluate a case.A landlord is responsible if people are injured on its premises, due to factors within its control, if the landlord was negligent, or unreasonably careless. Securing (or not) the air vents is within it's control; and not securing them down may well be considered negligent (especially if there are families with young children in the complex). If they are liable, they are potentially liable for medical costs; for lost wages (if you missed work to care for you child); and possibl for pain and suffering.