When you say 28 sec heating oil, are you referring to Red Diesel or to
paraffin?
If the later then it is OK to burn direct in the greenhouse, but diesel has
a sulphur content that is to high. If in doubt find out the oil company and
ask them.
When we had BP refinery close to us here I phoned and was given all the
facts and figures within 10 mins...and 5 of those were getting through to
the right person.
I am sure you could Email the company concerned and get a reply quite
quickly

--
David Hill
Abacus Nurseries
www.abacus-nurseries.co.uk