Technologies are generally described for gas filtration and detection devices. Example devices may include a graphene membrane and a sensing device. The graphene membrane may be perforated with a plurality of discrete pores having a size-selective to enable one or more molecules to pass through the pores. A sensing device may be attached to a supporting permeable substrate and coupled with the graphene membrane. A fluid mixture including two or more molecules may be exposed to the graphene membrane. Molecules having a smaller diameter than the discrete pores may be directed through the graphene pores, and may be detected by the sensing device. Molecules having a larger size than the discrete pores may be prevented from crossing the graphene membrane. The sensing device may be configured to identify a presence of a selected molecule within the mixture without interference from contaminating factors.

A kit for determining if a shock treatment is required for a water source may comprise a test strip having at least two chemically treated test areas. One of the areas is responsive in color to a concentration of free chlorine in the water and another test area is responsive in color to a concentration of total chlorine in the water. A chlorine indicator scale may be provided on a substrate, such as a label, and comprises a plurality of pairs of colored indicia and each pair of colored indicia representing a color pattern indicating a concentration, or range of concentrations, of total chlorine and free chlorine in the water. An alphanumeric designation may be provided adjacent to each pair of indicia indicating whether a shock treatment is required for the water source based on a color pattern the associated indicia pattern.