Important information about incomplete combustion and negative air pressure.
  A furnace does not produce carbon monoxide unless you have incomplete combustion. This is caused by your natural gas and air mixture in the combustion chamber not being checked or set up to manufacturers specification. Negative air pressure in your home can also cause this.
  Carbon monoxide can only enter your home if you have a cracked heat-exchanger, improper venting or improper ventilation or combustion air.
 A heat recovery ventilator that has not been properly balanced could cause a negative pressure in the house. With newer homes today being so well sealed up, negative air pressure can cause air to be pulled down a chimney causing a back draft of fumes. This negative air pressure could also be caused by air-moving stoves or basement exhaust systems even bathroom fans.
 Sulphur dioxide emissions are very bad for the environment and are also caused by incomplete combustion.
 You should ensure your maintenance people are fully licensed in natural gas and preferably ventilation also.
 Incomplete combustion can also raise your heating bills because un burnt gas is going up the chimney.

Important information about relative humidity in your home.
 Have your home relative humidity checked to ensure your home is not dry.
Dry air causes you to feel cold regardless of how warm you keep your house. (increased heat bills)
40 to 45% relative humidity is about right.
If your relative humidity is above 60%, mold starts to grow. Airborne mold spores are very dangerous. to your health.

Important information about furnace checks.
 To protect your heat exchanger, always have a "heat rise" done on your furnace.
Make sure that your limit and gas manifold pressure are checked during your maintenance
and also that your flame sensor is cleaned.
Always have a carbon monoxide check done and your venting inspected.
Ensure that a CO2 check is done because cracks in a heat exchanger are hard to see and your furnace may
be giving you high doses of CO2 and other substances. Since carbon monoxide is produced from incomplete combustion  you must ensure you always have enough air for combustion. "Ventilation Air"

Important information about indoor air quality.
One of the least understood concepts about indoor air quality is the importance of  relative humidity in your home. If the relative humidity is over 60%, harmful mold and other bacteria can start to grow. This is a common problem with newer homes because they are so airtight. If you think of yourself as living in a plastic bag, any moisture you put into the air by cooking, washing or showering, never leaves unless you have some type of air exchange. Heat recovery ventilators are ideal for this because they sense when the air is wet and then exhaust this air. The incoming air is pre heated by the exhausting wet and stale air. This air is very dry when warmed up by the furnace and quickly drops the moisture level in the house. If it runs on low speed continuously it will also keep your air fresh. This gets rid of chemical pollutants like vinyl and plastic vapors.
 If your house is too dry, you start to feel cold even though your house is 70 degrees. To prevent this you should only use the new flow-thru style of humidifier. This way you don't have a sump of warm water in your air stream in which bacteria can grow.
 There are many ways to clean your air.
 The best way is an electronic air cleaner which can do down to .01 microns with some brands. Some Hepa filters claim to filter out even smaller particulate but you have the added expense of changing the filter. There are also infrared lights which kill any living organisms and are ideal for keeping wet air conditioning coils sterilized.
 The following are examples of approximate particle size:
  Large particles like hair and pollen are 100 microns in size  Bacteria and mold spores are from 10 microns to .1 microns.  Smog, dust and tobacco smoke are from .1 to .01 microns in size
Important information about air conditioning
Note: Your new air conditioner should contain the new ozone friendly refrigerant "PURON" because R-22 is becoming obsolete. If the refrigerant charge is properly setup by a refrigeration mechanic you will have reduced hydro consumption and longer compressor life.
Your system upon installation should be vacuumed to below 300 microns to ensure there isn't any moisture present which will cause acid. This acid breaks down your compressor and it is hard and expensive to re-clean your system.
Your refrigeration charge should be set up with a "sling psychrometer" to the manufacturer specifications.
Ensure your evaporator and condenser coil cleaned.
A dirty condenser can increase your hydro consumption by 60% and greatly increase breakdowns.
All air conditioners manufactured after 2006 must be 13 seer. (Seasonal energy efficiency ratio)
An air conditioner that is hooked up to the intelligent furnace system can control the amount of humidity the
air conditioner takes out of the air.