What would cause excess CO2 in cellar
If you're feeling lightheaded/out of breath in the basement, I'd stay out of there until it's well ventilated and never enter the area without someone on the outside to monitor  you and call for help if needed (but that person should not enter the area). If it were my basement, I'd call the fire department to check for Carbon Monoxide and/or combustible gas and assist with ventilation.

One possibility is that Carbon Monoxide has accumulated in the basement, perhaps due to a faulty heating appliance and poor ventilation, or gasoline powered equipment in or near the house. This is extremely hazardous and potentially fatal -- it can cause you to become incapacitated and unable to leave the space. 

Some signs of CO exposure include:


  Headache
  
  Shortness of breath
  
  Personality changes
  
  Unusually emotional behavior or extreme swings in emotions
  
  Fatigue
  
  Malaise (a generally sick feeling)
  
  Dizziness
  
  Clumsiness or difficulty walking
  
  Vision problems
  
  Confusion and impaired judgment
  
  Nausea and vomiting
  
  Rapid breathing
  
  Chest pain
  
  A rapid or irregular heartbeat


Another, less likely possibility is Carbon Dioxide (CO2). CO2 is heavier than air and can pool in low areas such as unventilated basements. It would take a fairly high concentration of CO2 to prevent a match from igniting. It is less dangerous than CO in that the CO2 doesn't bind to your blood like CO, but overexposure to CO2 can incapacitate you, preventing you from leaving the area.

CO2 can be generated by a combustion appliance like a natural gas or propane fueled dryer or heater with a faulty exhaust vent. Other sources could be something  that uses CO2 gas directly like gas from MIG welder, home brewing equipment, home water carbonator, etc.

You could have a natural gas/propane leak. I'd avoid any open flame or anything  else that serve as an ignition source (wuch as turning on a switch or even a flashlight) just in case  the problem is caused by a combustable gas. Propane is also heavier than air and can pool in lower areas (Natural gas is lighter than air and tends to dissipate, except when the gas is cooler than air and more dense, so  it can pool). It is possible for the odorant used in natural gas and propane to  fade, so lack of distinctive gas odor doesn't necessarily mean that  no gas is present.

There are certainly other gases that could also be causing the problem such as sewer gases, or other gases that come from the ground, or heavier than air gases that are released anywhere near the house.