I think they were more scientific and well planned.The newer ones are shoddy with bad materials and poor engineering which are causing pollution scares all over the world.  Www.newjerseyairconditioning.com

Carbon dioxide is heavier (more dense) than oxygen. About 8 CO₂ molecules weigh the same as 22 O₂ atoms.

" … Read more

The car emits carbon monoxide which is a problem.The fuel that is necessary is also scarce and so that is another problem.But scientists are working on it....to replace fuel with bio gas and also emissions lessened through electric cars.

The major types of pollution are air,water,thermal,land,noise radioactive and thermal pollution.new jersey air duct cleaning