The **rear fog lights** are a type of light used in situations where visibility is very limited. These lights are red and are designed to improve the visibility of the vehicle from behind in adverse conditions.

- **Conditions of use:** Rear fog lights should only be used when weather or visibility conditions are extremely poor. This includes situations such as **dense fog, snow, heavy rain, and thick smoke clouds**. These conditions can make it difficult for other drivers to see your vehicle, so rear fog lights help make your vehicle more visible.

- **Importance of smoke:** In the specific case of **thick smoke clouds**, rear fog lights are essential to ensure that other drivers can see your vehicle in time and avoid accidents. Smoke can drastically reduce visibility, similar to fog, and that is why it is crucial to use these lights in such situations.

Therefore, it is correct to use rear fog lights in the event of **thick smoke clouds** to improve road safety.