There are a number of commercially available electronic H2S sensors that can be installed in the line between the gas cylinder and your test chamber to continuously measure in a wide range of H2S concentrations measured in ppm.  A good review of the available sensors can be found in "A review of sensor-based methods

for monitoring hydrogen sulfide" by Sudhir Kumar Pandey, Ki-Hyun Kim, Kea-Tiong Tang in Trends in Analytical Chemistry, Vol. 32, 2012.

You can also use one-time use chemical sensor tubes for checking H2S concentrations.  These tubes are often called Draeger tubes based upon the company that sells most of them.  These tubes only work at atmospheric pressure and require the removal of a small volume of gas from your system to measure the H2S content.  These tubes can be purchased to measure in the ppb range and can also less expensive to use when only a few are required.

If you can take a sample, an Orsat apparatus could be used for this measurement. Those are cheap and very simple in use. Though with H2S you should be careful not to have leaks. http://en.wikipedia.org/wiki/Orsat_gas_analyser

you might also consider using a sampler with a DIPA solution or NaOH to absorb the H2S.  Its then easy to analyze the H2S titrimetrically and have your results in ppm.

Lim

Can you explain or email the details of this solution and sampler? I have another idea how It might be accomplished

one of the most common measurement methods for H2S concentration of gas stream is Tutwiler method.

You might use the gas detector tube, and you can find this article as the reference!

https://www.sciencedirect.com/science/article/pii/S0003267009013518

1. The Dräger Diffusion tubes are direct reading systems used for the determination of time weighted average concentrations over the duration of one to eight hours. Direct-reading diffusion tubes are used specifically for personal exposure monitoring.The Diffusion Tubes are very easy to handle. Since these are passive measurement systems, relying on the diffusion of contaminant molecules in air, they do not require a pump. The diffusion tubes are used with a plastic holder which is attached to the clothing. The Dräger Diffusion Tubes are able to measure very low as well as High concentrations. The contaminant molecules pass into the tube by diffusion processes and are brought into contact with the reagent systems. The measurement result can be read directly on the scale printed on the Diffusion Tube, Drager-Tubes contain a chemical reagent that changes color when it comes into contact with a gaseous substance (colorimetric). The tubes’ fused ends give them a shelf life of two years and keep the gases contained. A printed scale on the outside of the tube allows for a direct reading of the gas concentration.

2. You can install on line sensor available in market. There are a number of commercially available electronic H2S sensors that can be installed in the line between the gas cylinder and your test chamber to continuously measure in a wide range of H2S concentrations measured in ppm.

3. By Titration DEPA Solution or NaOH by absorbing of H2S.

4. ByTutwiler method.

5. Use one-time use chemical sensor tubes for checking H2S concentrations. These tubes are often called Draeger tubes based upon the company that sells most of them. These tubes only work at atmospheric pressure and require the removal of a small volume of gas from your system to measure the H2S content. These tubes can be purchased to measure in the ppb range and can also less expensive to use when only a few are required

6. In some areas it is possible to purchase pre-mixed CO2/H2S in gas cylinders with desired H2S concentrations, However, when talking about low ppm levels, the requested H2S concentration in the gas may only exist at the suppliers facilities as the gas is being mixed. In the time between being mixed and eventual use, the gas will slowly react with the steel cylinder. This will result in slow drop in the H2S level. How fast this occurs will depend on if the cylinder has seen past H2S service and the storage temperature and transportation temperature.Therefore, to know the H2S concentration of the gas, you really need to run a GC analysis at the same time as your test. If you don't do this, instead of haviang 10ppm, the level could be something lower. I have seen CO2/200ppm H2S gas drop from 200 a the time of delivery to around 120ppm a month or two later.That is one of the reasons why I used a continuously metered stream of CO2, Na2S and dilute HCl and brine when I conducted my low H2S autoclave testing. We then did periodic dissolved H2S analyses of the fluid flowing out of the autoclave. This is the only way that we could figure out to be certain of the exact H2S levels that we were using in my tests.

7. You can order eg. 20 ppm H2S in synthetic air, the level of H2S before and during experimental tests measure the flue gas analyzer.