A protective helmet having an impact-resistant outer shell with an impact liner disposed within. The impact liner encloses a substantial portion of a wearer's head. A fan assembly having at least one fan and preferably a fan cowling is disposed between the impact liner and the outer shell. In operation,...http://www.google.es/patents/US6081929?utm_source=gb-gplus-sharePatente US6081929 - Impact protection helmet with air extraction
