One of my clients has just had their spray booth staturtory examined and tested, and the report states that it has passed and captures the hazardous substances; yet the enfineer has failed it becasue he says there is no DSEAR risk assessment regarding ignition sources. 

There is a DSEAR risk assessment; there are no ignition sources in or near the spray booth; the fan is a bifurcated fan, suitable for the the job. My question is since the examination and test is a requirement of COSHH and it passes, how can he fail it as surely this is not in his remit

This is the issue with inspections: what do you test against? The guy was doing an inspection against some standard which includes the DSEAR element. It failed the test because of this.  But it looks like you are not interested in DSEAR element so the kit is being over tested for what you want. Usually it’s the other way around: LEV are often inspected and tested but only for the airflows etc not necessarily how effective they are at containing the contaminants you are using.

You need to be clear what you want the testing people to test for  ?