Wasps and the hi efficiency heating system...
 

Do any of you experts in the gas/ forced air heating system busines know what to do about wasps getting in? During the summer I heard something in the ducting in the basement but was not sure what it was. Recently the furnace has started cutting in as it has cooled off enough. Now coincidental with that time we found about 15 wasps lying in a 2 foot radius in a basement room in the vicinity of three pipes - first pipe is pvc inlet, 2nd is pvc outlet and the third is for the water heater air inlet.

Now the only screen is on the water heater inlet but has a mesh on it but is not fine enough to prevent wasps getting in. Apparently it is not allowed to put mesh screening on the pvc pipes because of ice buildups. Capping off the pvc pipes in the summer is a possibility but must be removed before furnace start up.

Now if the wasps can find a way out when furnace heat kicks in and they likely die of carbon monoxide poisoning then how do they find a way of getting out? A hole in the ducting somewhere? Then there is a risk of getting co poisoning? I will get a new CO detector for starters. Any ideas on keeping wasps out and and how would wasps find their way out and where?

Wow that's weird. If they came in through the pvc venting I can't see how they would wind up on the floor. The venting(pvc) should be sealed from outside to the furnace/water heater.
They could of come in somewhere else. Pictures would help.

A/C condensation drains maybe? The A-coil just sits on a pan that collects water, the drains connect to the pan and take the water to your floor drain (typically). That portion is open to your basement, the sealing around the A-coil is rarely all that tight.

They likely died from the heat of the air in the furnace and a lack of oxygen in the hot thin air. But a co2 detecter is alway good to have around the house.