Carbon monoxide (CO) at high concentrations is extremely poisonous to humans and other invertebrates. It is one of the leading causes of unintentional deaths in the United States. Furthermore, people with heart diseases are more vulnerable to high CO levels since they already have a reduced ability to get oxygenated blood to their hearts. Functional nanomaterials (metallic nanoparticles [NPs], carbon nanotubes [CNTs], and nanofibers [NFs]) offer a high surface area, low weight-to-volume ratio, flexibility, and high porosity, which are perfect properties for gas absorption. Many nanomaterials are currently playing an essential role in CO-capturing technologies. This paper focuses on the usage of those functional nanomaterials for CO absorption and their absorption mechanisms. Due to high surface area and porosity, these materials have been widely used to absorb pollutants, including toxic gas like CO. Fabrications, CO-absorbing mechanisms, and absorbing properties of some nanomaterials will be discussed here.