Methods to systematically analyze in parallel the function of multiple protein or cell samples in vivo or ex vivo (i.e., functional proteomics) in a controlled gaseous environment have so far been limited. Here, we describe an apparatus and procedure that enables, for the first time, parallel assay of oxygen equilibria in multiple samples. Using this apparatus, numerous simultaneous oxygen equilibrium curves (OECs) can be obtained under truly identical conditions from blood cell samples or purified hemoglobins (Hbs). We suggest that the ability to obtain these parallel datasets under identical conditions can be of immense value both to biomedical researchers and clinicians who wish to monitor blood health and to physiologists who are studying nonhuman organisms and the effects of climate change on these organisms. Parallel monitoring techniques are essential in order to better understand the functions of critical cellular proteins. The procedure can be applied to human studies, where an OEC can be analyzed in light of an individual's entire genome. Here, we analyzed intraerythrocytic Hb, a protein that operates at the organism's environmental interface and then comes into close contact with virtually all of the organism's cells. The apparatus is scalable and establishes a functional proteomic screen that can be correlated with genomic information on the same individuals. This new method is expected to accelerate our general understanding of protein function, an increasingly challenging objective as advances in proteomic and genomic throughput outpace the ability to study proteins' functional properties.