CO2 sensor for low volumes

I see there is an evaluation kit available:

https://www.farnell.com/datasheets/3190557.pdf

https://www.farnell.com/datasheets/3190558.pdf

For this interface board:

media.digikey.com/.../QGS_Series_DS.pdf

www.mouser.com/.../KEM_SE0220_QGSM-2529518.pdf

The undetailed datasheet is quite annoying, or maybe it just states that the sensor is just a "ON / OFF" type, so the datasheet just describes in which LED working frequency range is more effective.

Couldn't find it at higher-res: 

There is also an evaluating kit sold, which is basically the LED and the tube already built, which could save me a lot of hassle. It doesn't specify how powerfull should the LED be, it should depend on the NEP right? It states 2.7*10e-10 on the cheaper one, and "mean 70" on the dual sensor one. What ranges should I look for, in case I really wanted to go down that road?

I would get in touch with Sensiron

Oh, I think I replied to the wrong parent comment, I was talking about the KEMET. But for sure, I will get in contact with them.

Last thing I'm asking, what kind of LED should I couple with the KEMET?
https://www.mouser.it/ProductDetail/KEMET/USEQGSM1C82100?qs=xZ%2FP%252Ba9zWqYuG7UZtSVO%2FQ%3D%3D
I've roamed around Mouser for the last couple days, and I'm just getting more confused.
The NEP is 2.7*10e-10 while the D* is 2.5*10e8.
www.mouser.it/.../KEM_SE0220_QGSM-2529518.pdf

The only graphs I see doesn't clear up things for me

Thanks a lot for any hint!

I would use the info on page 3 of 2nd pdf... states:

KEMET Infrared Sensors work in the MID Infrared Spectrum.

Then transmit strength is also relevant as depends on distance between led and sensor within enclosure.
Understanding how much IR is being optically transmitted versus how much is received can
indicate gas concentration levels.

Hey! Thanks for your answer.
I was already looking into mid IR spectrum emitters, the strenght itself is my concern, that's why I was looking on how to interpret the NEP or the Detectivity. I can't really land on a definitive conclusion. Maybe I shall just buy emitters in a broad range and try which fits better.

Personally, I would use the evaluation kit, which according to page 9 of that 2nd PDF uses a TO39 (pulsable?) type IR emitter... not that that gives any clues on transmit strength but at least if you had similar it should work.

Mid wavelength IR is thermal. It may be too expensive to buy a range of emitters. Any emitter in that range should work. The sensor also seems to specify the IR be collimated. If collimation requires a lens, it could get expensive, since lenses for these wavelengths are not made of glass or plastic. Hopefully the emitter will have a collimating lens built-in.

Wow, yes having searched online I see these IR emitters are highly specialised (i.e. pricey). I see these ones I found use reflectors
www.micro-hybrid.de/.../