Charlotte, I know vegetable oil contains an anti-oxidant,(to prevent the oil from going rancid) and an anti-foaming agent, but have never come across a fire retardant in the vegetable oil.
When people were setting their vehicles up to utilise waste oil, the big oil companies started making some ridiculous claims,that it couldn't be done, well I have 10,000 miles up now running on waste cooking oil and the diesel doesn't blow any smoke. I pulled the injectors last weekend to check for any carbon build-up and there was none, it would be a different story if the oil entered the engine cold, but if you faithfully follow the protocols for running waste vegetable oil you shouldn't have any problems.
The LucasCAV injection pump is a worry though, it seems to have the least tolerance of any pump for vegetable oil. If I was going to set up using the LucasCAV pump I would use a blend and still try to get the oil as hot as possible.
If anyone is interested there is greasecar forum in the USA , just do a google search, I occassionally contribute my experiences and opinions to this forum.There are some very experienced people there who make and design kits and have a lot of experience on this topic.
Kind regards...Ron.