A blower with a filter is mounted on {HEAD ~ the outside} of {TAIL ~ the desk} and blows clean air into the compartment 
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A blower with a filter is mounted on { HEAD ~ the outside } of { TAIL ~ the desk } and blows clean air into the compartment
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH