• Mold can grow on almost any surface in your home.mold on petrified wood image by MAXFX from Fotolia.com
  
  Mold is a variety of plant responsible for decaying organic matter in nature. Mold tends to grow in dark and damp places such as your basement, bathroom or in furnace ducts. This is especially true for homes in humid climates. Some types of mold can cause serious long-term health issues in susceptible individuals such as the elderly, pregnant or those with respiratory difficulties. Check your duct for symptoms of mold periodically to prevent these issues from affecting you and your family.
  
  

Visible Growth

• Perhaps the surest sign of mold growth in your home furnace ducts is visible growth. Different types of mold have different appearances. Some can appear white and powdery while others are black and slimy. Color ranges from white to green to black and texture ranges from bumpy and powdery to slimy. Mold growth is composed of hundreds of microscopic spores. Thus, visible mold growth is only a sign that there is a significant amount of mold on your home furnace ducts.
  
  

Smell

• Most types of mold have a musty or dank smell. This is especially true when the mold is in a small area such as a crawl space or in your home furnace ducts. In these cases, the mold smell may be particularly pungent. Smelling for mold is especially important for home furnace ducts, as you will be unable to see deep into the duct to check for mold.
  
  

Health

• Sometimes you may be unable to see or to smell the mold growth in your home furnace ducts. The third symptom of mold growth, which may help you locate it, are the irritations it may cause. For some, exposure to mold can cause a runny nose, watery eyes or shortness of breath. However, these symptoms may not always be an accurate symptom as these are also common for those with seasonal allergies or dust or dust mite sensitivity.