Smoke Demystified

There are several different kinds of smoke, each which requires a different type of cleaning process. Here’s our handy guide to help you classify what type of smoke you’re dealing with.

Smoke Classification

There are two different types of smoke: driven smoke and free-floating smoke.

Driven Smoke, also known as hot smoke, is pressurized and has energy behind it. The smoke residue found on vertical surfaces results from driven smoke.

Free Floating Smoke, also known as cold smoke, started as pressurized smoke but has lost the energy and velocity behind it. Because free floating smoke is heavier than air, it often settles on horizontal surfaces. Horizontal surfaces are the single biggest source of smoke odor.

Within these types, there are three main categories of smoke odor: protein, natural substance and synthetic substance.

Protein Odors: Result from burned flesh/meat. The residue from protein odors is yellow/brown and has a greasy texture.

Natural Substance Odors:  Result from burned wood, paper, cotton, wool, cork, feathers, etc. The residue from natural substance odors is gray/black and has a dry, powdery consistency.

Synthetic Substance Odors:  Result from burned plastics, synthetic textiles, etc. The residue from synthetic substance odors is black and smudges easily.

What kind of smoke did my fire produce?

It depends on the duration of the burn and which substances were influenced. Smoke residues from natural fires are generally easier to clean up than a protein or synthetic fire. For example, it would be easier to clean up the residue from a wood or paper fire than it would to clean up the residue from a fire of synthetic or protein origin. Here’s a brief introduction, but please feel free to contact us for a more thorough analysis.

Low Oxygen Fires: Are smoldering, long duration fires which produce a difficult to remove wet smoke residue.

High Oxygen Fires: Burn more efficiently and produce an easier to remove dry residue.

Corrosive Nature Fires: Smoke residues are generally acidic in nature and often cause corrosive damage to metal surfaces. To prevent corrosion to metals, smoke residues should be removed as quickly as possible. When burned, PVC plastic produces highly corrosive PIC’s (particles of incomplete combustion), which combine with atmospheric moisture to form hydrochloric acid.  

What Influences Smoke?

  • Heat – Warm air rises and migrates to cold areas (outside walls, closets, etc.) Heat causes pores to expand.
  • Pressure – The energy created by a fire produces heat and pressure which enables the smoke to penetrate into minute cracks and crevices.
  • Impingement –  Means splatter, when a substance hits a surface with sufficient velocity it will impinge (or splatter) and remain upon that surface.
  • Magnetism –  Attraction of smoke to metal surfaces. (Plumbing pipes, nail heads, metal coat hangers).
  • Ionization –  Opposite charges attract, forming smoke webs on structural surfaces.  Plastic bags from the dry-cleaners retain static electrical charges which attract smoke.  In fact, in many fire situations, more smoke residues will be found on garments protected by plastic bags, than found on unprotected garments.
  • Air Currents – Smoke is aided by both natural and manmade air currents. Natural convection currents of air rise when heated and fall as they cool. Forced air heating and cooling systems can spread smoke odor over a wide area.

Factors Affecting the Degree and Amount of Smoke Residue

         1)  Substance burning

         2)  Amount of available oxygen i.e., type of fire smoldering versus well oxygenated

         3)  Duration of the fire

         4)  Temperature and penetration potential of the fire

         5)  Air currents

         6)  Method of extinguishment

         7)  Type of HVAC system

         8)  Building layout and design

Smoke odors are most apparent when both temperature and relative humidity are high.