An apparatus includes a container that defines an interior. The interior is isolated from ambient atmosphere for receiving a composition that includes isocyanate. A conduit extends into the container and defines a channel therethrough. An interior of the container is in fluid communication with the ambient atmosphere through the channel for conveying a gaseous waste stream that includes vaporized unreacted isocyanate out of the container and into the ambient atmosphere. A medium is disposed in the channel and has free isocyanate-reactive groups for reacting with unreacted isocyanate. The free isocyanate-reactive groups remove the unreacted isocyanate from the gaseous waste stream. The medium, by including the free isocyanate-reactive groups, relies on a chemical reaction to remove the unreacted isocyanate.