I understand that the exhaust vent from a brand new energy efficient gas furnace contain an acidic content. Is that correct? If so, how dangerous is it to breath that vapor in. My reason for asking is that I live in an old neighborhood where the homes are very close to each other. My neigher just converted from Oil to Gas and their new exhaust vent from their new gas furnace vents approx 6 feet from my driveway and the exhaust generally fills my driveway like fog and I breath that in when I am in my driveway. How dangerous is that?
Thanks for your time.
Exhaust from any combustion source is always a good idea to avoid breathing. The major byproducts of natural gas combustion are water vapor and carbon dioxide, which are harmless. Minor byproducts can include carbon monoxide, various oxides of nitrogen (NOx), sulfur dioxide (SO2), and various hydrocarbons. The primary concern is carbon monoxide, which I'm sure you know all about.
The "acidic content" you may be referring to could be the NOx components. On a global scale, NOx emissions from many sources (vehicle exhaust, industry, power plants, etc.) react with water vapor and form acid rain. From a personal exposure standpoint, from one source-point exposure, the acidic potential of NOx combination with water vapor is not a concern. The biological reaction to the inhalation of high levels of NOx (such as being in a room with an unvented propane heater), would be upper respiratory irritation and airway constriction, perhaps an asthtamtic type response.
I can't accurately answer "how dangerous is that" with the information given. In general, it's best practice to vent exhaust upwards and away from human-occupied areas. Also look into local building code and see if your neighbors exhaust flue is in compliance. If it's not, that could be an easy way to force them to fix it. Just call your city code compliance officer, make the complaint, and they will take care of the inspection and any required corrective action enforcement.