Disclosed is a method for collecting hydrocarbon vapors before they are dispersed in the atmosphere surrounding a site where loading or unloading of flammable fuels occur. The collected vapors are monitored to determine when the air-hydrocarbon vapor mixture is near or in the combustible range. When it is determined that the mixture is near or in the combustible range, a hydrocarbon gas such as propane is injected into the mixture to remove the danger of explosion or fire. The collected vapors are held in a holding tank and, preferably, are periodically burned.