In a closed circulating gas system having a pump which draws gas at an inlet from a return line and delivers {HEAD ~ gas} under pressure at an outlet to a supply line, and also having a load device which receives gas from the supply line and delivers it to {TAIL ~ the return line}, apparatus for detecting leaks in the system comprising: 
In a closed circulating gas system having a pump which draws gas at an inlet from a return line and delivers { HEAD ~ gas } under pressure at an outlet to a supply line , and also having a load device which receives gas from the supply line and delivers it to { TAIL ~ the return line } , apparatus for detecting leaks in the system comprising :
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH