1. A method for providing a sensor for presence of at least one of a first selected gas molecule and a second selected gas molecule, the method comprising: providing, in a chamber, first and second interdigitated electrodes, which are connected to at least one of (i) a voltage source having a controllable voltage difference and (ii) a controllable current source; providing a zeroth order electrically conducting network, numbered 0, of uncoated single wall carbon nanotubes (“SWCNTs”) forming a path P0 between the first and second electrodes; providing N electrically conducting networks, numbered n=1,. .. , N (N≧1) of single wall carbon nanotubes (“SWCNTs”) forming paths Pn (n=1,. .. , N) between the first and second electrodes, where at least one SWCNT in each of the networks no. n (n=1,. .. , N) is loaded with molecules of a selected chemical no. n; providing in the chamber a gas G that may have molecules of a gas constituent no. m present in a concentration C m (m=1,. .. , M; M≧1), where at least one of the concentration values C m is unknown, allowing at least one molecule of the gas G to become absorbed on at least one of the SWCNTs in each of the paths P0 in the zeroth order network and Pn in the network number n (n=1,. .. , N); providing an electrical parameter value (“response value”) V 0 (G;meas), associated with the path P0, of at least one of (i) electrical current, (ii) electrical conductance, (iii) voltage difference and (iv) electrical resistance associated with the path P0, when the gas G is present, and providing a corresponding response value V n (G;meas), associated with the path Pn (n=1,. .. , N) when the gas G is present; adding a known concentration increment Δ 1 C m0 of a gas constituent no. m0, selected from among the M constituents, to the gas G to provide an augmented gas G′, allowing at least one molecule of the gas G′ to become absorbed on at least one of the SWCNTs in each of the path P0 and Pn (n=1,. .. , N), and providing corresponding response values V 0 (G′;meas) and V n (G′;meas) for the gas G′; comparing differences, V n (G;meas)−V 0 (G;meas) and V n (G;meas)−V 0 (G′;meas) (n=1,. .. , N) of the response values and estimating at least one of (i) concentration and (ii) concentration upper bound and (iii) concentration lower bound for at least one of the first gas molecule and the second gas molecule present in at least one of the gas G and the gas G′ wherein the process of estimating at least one of (i) the concentration C and (ii) the concentration upper bound and (iii) the concentration lower bound comprises: providing an error function ε(C 1 ,. .. , C M ), defined by 
 2ε( C 1 ,. .. , C M )=Σ n w n ·{V n ( G ;meas)− V 0 ( G ;meas)−Σ m a n,m C m } 2 +Σ n w′ n ·{V n ( G′ ;meas)− V 0 ( G′ ;meas)− a n,m ( C m +ΔC m )} 2 , where a n,m is a response value coefficient relating change in the response value V n (G;meas) to change in the concentration C m of the constituent no. m, ΔC m is a known concentration increment of the gas constituent no. m, added to the gas G to provide the gas G′, w n , and w′ n are selected non-negative weight values, and at least one increment value ΔC m is positive; forming M partial derivatives of the error function 2ε(C 1 ,. .. , C M ) with respect to the concentrations C 1 ,. .. , C M , to provide M non-homogeneous, linear equations relating the concentrations C 1 ,. .. , C M ; solving the M non-homogeneous linear equations to provide values, C m (min) for the concentrations C m as solutions of the equations; and associating at least one of the values C m (min) with an estimate of the concentration of the constituent no. m in at least one of the gas G and the gas G′.