Describe the procedure for placarding a container containing multiple dangerous goods with differing hazard classes.

When a container contains multiple dangerous goods with differing hazard classes, the IMDG Code requires that the container be placarded with all the hazard placards corresponding to the primary hazard of each dangerous good present, with certain exceptions. Placards are diamond-shaped symbols that visually communicate the primary hazard associated with a particular class of dangerous goods. For example, if a container contains both flammable liquids (Class 3) and corrosive substances (Class 8), the container must be placarded with both the Class 3 flammable liquid placard and the Class 8 corrosive placard. Placards must be displayed on all four sides of the container, and they must be clearly visible and legible. There are exceptions to this general rule. If the container contains subsidiary hazards that are already indicated by another placard, the subsidiary hazard placard may not be required. For example, if a substance is both flammable and toxic, but the flammable hazard is the primary hazard, only the flammable placard may be required. Also, if a container contains multiple dangerous goods that all fall under the same hazard class, only one placard for that hazard class is required, even if the goods have different UN numbers. The dangerous goods in "limited quantities" exception also affects placarding. If the dangerous goods are packed in accordance with the limited quantity provisions, the container does not need to be placarded with individual hazard placards, but it must display the limited quantity mark on all four sides. Following these rules ensures that the container is properly identified and that handlers are aware of all the hazards present.