You didn't specify the country for this application, the industry, or the classification, so it's difficult to answer very directly. You might contact one of the analyzer companies such as Ametek, Siemens, or Yokogawa and ask them to supply analyzers to your client. They have been doing this for a long time and understand the instruments.

How did you get this job without any qualifications?

Ah well. Not for me to reason why.

I recommend google. It will answer most of your questions. If you learn to ask it quick, you might even keep this job.

It sounds as though you have your work cut out for you. If you can remember only one thing, let it be that 1% = 10,000 ppm. So, 10% would be 100,000 ppm, etc. You will need to determine whether the concentration is by weight or volume. Talk with the instrument manufacturers to fill in the blanks.

You are at the bottom of a steep learning curve.

Welderman has already address the ppm vs % question.

Most of the low cost analysers (less than £8,000) measure the proportions bassed on volume and you have to convert to weight if necessary.

The 0-1% and 0-10% refer to the ranges available as do the 0-500PPM, 0-1000 PPM in another enquiry for Hydrogen measurements.

Get hold of a range of analyser manufacturer's literature and read up the subject. Try googling testo. They have some interseting stuff on their site.