the reader needs to conceptually expand its concentration into its concentration in the air in the interior of the car, and hazard into hazard for occupants of the car. In this example, lexical knowledge to the effect that concentration (in the chemical sense)  refers to the concentration of some substance in some medium could at least provide the “slots” that need to be filled, and a similar comment applies in the case of hazard. However, not all of the fillers for those slots are made explicitly available by the text—the carbon monoxide referred to provides one of the fillers, but the air in the interior of the car, and potential occupants of the car (and that they rather than, say, the upholstery would be at risk) are a matter of inference from world knowledge.