Answer:
Toxic fumes are gases that are poisonous or dangerous to people. There are different levels of toxicity, meaning some fumes ( gases ) are more dangerous than others. For instance, carbon monoxide can be present in your house. It is a toxic fume that comes from car exhaust or furnaces. In very, very low concentrations, you may only show mild symptoms like a headache or even none if you come and go a lot. But in higher concentrations it will be lethal (deadly ) and kill you.
Toxic fumes generally come from factories or result from chemical processes like combustion ( in an engine ), or processing/manufacturing ( mills, oil refineries,chemical plants). It is now widely accepted that cigarette smoke is toxic, as it causes cancer, and has been linked to lung and heart diseases. Generally, most toxic fumes are man-made.