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Crude process, but does the trick: You can use a combustion/oxygen consuming process, like a candle, to burn the excess oxygen. Eventually the candle will be too oxygen starved to sustain a flame, so some residual oxygen would be left (although this would already mean there is no fear of combustion of said tyres). Now to remove the remaining oxygen you'd use something like iron files (since you wanted to use only "household" stuff). Together with some humidity in that air, they will rust rapidly and should drive down the oxygen contents towards negligible. So now we have: a) a small trace remainder of oxygen, b) the equivalent of CO2 from the combustion process, d) some impurities from the candle wax probably, e) trace gases such as helium etc. and ... mostly f) nitrogen. This already is not sustaining any combustion. But if you're a purist or want to use N2 because it is lighter than CO2 ... To remove the CO2 you could use something like "roasted limestone", i.e. the stuff from you water kettle, which you heat so that you get lime, which then binds with the CO2 to revert to limestone CaCO3. Now you have something, I'd assume, like 98% nitrogen and surely to few traces of O2 to cause any harm to your equipment. Of course, I'd buy bottled N2, but for the sake of using household implements only, this might do the trick.