# Changing the CO2 concentration (adding or subtracting) inside a sealed vessel?

I am looking for a method of modifying the CO2 concentration inside a sealed container that is both precise and repeatable (C02 needs adjustment every time the container is sealed, also need to be able to make additional adjustments to counteract potential slow leaks.

Is there a way I could do this electrically? Voltage across a sample of some precursor? Coating a heating wire with something that could be gradually burnt off? I read an online article from 2016 about a type of battery that actually removed CO2 from the atmosphere and used it to generate a current (and in the process reduced the concentration) - could not tell from the article if all the parts of the battery were solid - if it were then perhaps a scaled down cell?

Very much appreciate any suggestions so I have some options.

• Without a lot more detail (how big is the container, what pressure do you need, over what timescale, what else is in the container, what is the container made out of, ...) this is really hard to answer. – Jon Custer Jan 16 '19 at 16:15
• size would level between envelope and suitcase size, - I'm working out a system to detect intrusion into a package or luggage - the idea I had was to modify the CO2 level inside once it was sealed so that upon opening the CO2 levels would rush back to normal ambient levels and a CO2 sensor would detect the intrusion. – norlesh Jan 16 '19 at 16:25
• I'm not prepared to give you a full answer, but maybe you should look into the membrane technologies. Existing carbon dioxide capture membrane prototypes are made of wide range of materials, including organic ones that work at fairly low temperatures (e.g. DOI 10.1021/ie070794r). As for the "battery," molten carbonate fuel cells can be used for $\ce{CO2}$ transport (e.g. DOI 10.1021/ie302725a). Anyway, it might be easier to pump the package with pure nitrogen, either from the gas bottle or from the generator, and detect the intrusion by measuring the oxygen partial pressure. – voffch Jan 16 '19 at 17:05
• @voffch - it turns out that CO2 sensors are more robust and cheaper than O2 sensors. For the OP, particularly since the container is not 'sealed', you likely will have some issues with shipping companies by having power, compressed gases, etc. inside the volume. There are other ways to see if something has been opened or not in transit. – Jon Custer Jan 16 '19 at 17:35
• Just to clarify the objective is a small battery powered device that drops inside the bag - no gas bottles - any reactants for creating the additional CO2 (only need enough to make a small relative percentage difference) need to start off in a solid phase and only a small battery will be available. – norlesh Jan 16 '19 at 20:36