Tips for QCL Carbonyl Sulfide 
Measurements

Many researchers use a quantum cascade laser (QCL) to make high frequency/high precision measurements of carbonyl sulfide.  

When using a QCL to detect ambient level OCS, two things should be taken into account: 
temperature should be as stable as possible and
moisture should not build up in the sample cell.

While having an air-conditioned room to house the QCL is a first step, further problems can arise with air vents blowing onto the lab bench or temperature fluctuations from opening and closing doors.    

Other researchers report ambient pressure effects for some QCL systems.

L. Kooijmans has used a separate CO2 analyzer to find a leak in the sample cell of the QCL by monitoring the analyzer exhaust.

W. Sun suggests using a buffer volume when doing chamber measurements in the canopy, because turbulence may cause ambient COS concentration to fluctuate rapidly.

Three companies make commercially available units that have been deployed in the field:
Aerodyne (Wingate, Commane, Seibt, Maseyk, Berry, Yakir, Wohlfahrt, Kooijmans)
Los Gatos Research (Still, Berkelhammer, LaFranchi)
Aeris Technologies (Meredith, Commane, Whelan). This last one is much less expensive (36k) but has yet to produce presentable data. We are hopeful.