t's very important for people to realize that in the event of a fire, the hazards are not always gone once the fire is put out. Toxic gases that continue to smoulder are a real danger. Even if the smoke appears to be gone, toxic products of combustion likely still exist in dangerous concentrations and can be very harmful to your body.
Carbon monoxide (CO) and hydrogen cyanide (HCN) are common toxic gases found, but countless others are often now found in today's modern homes. Also other non toxic airborne particles will be floating around in the air that we would not want to introduce into our respiratory system.
Furthermore, there will likely be physical damage to the structural components of your home. Possible damage to the floors and ceiling can cause them to weaken and become a dangerous concern. Not to mention debris like broken glass, nails, and other "sharp" hazards can cause harm.
Access to a home after a fire should only be made once the fire department has finished air monitoring, and deemed it safe to enter.