My home is 5 yrs old..The oil furnace is direct,power vented. We are getting exhaust fume smells in the basement and throughout the house.It does vary with the amount of the wind.We have had our oil man here 3 times. He has cleaned twice and checked for leaks and put his carbon monoxide sniffer near the unit and it does not show any traces.He thinks the wind is blowing the exhaust into the basement thru doors/windows and getting sucked into the air intake.The problem is-we have not experienced this in 5 years and nothing has changed in that time to cause it,that we are aware of. Additionally, the smell is strong on the outside of the house and yesterday I noticed that the shrub in front of the exhaust is brown and dead.Any help is appreciated.

Sounds like it needs to be tuned up/serviced. Does your unit have a name brand or a Exact model number so we can see exactly what you have?

It is a Thermo-Dynamics model S-100. It was "supposed to be"cleaned and tuned by the service man twice.....

I have no listing for that unit. I am in the USA and never heard of that brand or model before. Most furnaces work the same and from what you stated in your post the unit is running dirty causing excess fumes etc. Sorry but that is all the info I have.