I'm having a new exterior masonry chimney built. The mason has excavated and poured a footing attached to my foundation and started building up to ground level. He has also started laying clay flue tiles starting at the footing. The cleanout door will be somewhere above ground level with the thimble being 4 or 5 feet above that. This will leave 6-8 feet of flue below grade and below any cleanout. Does this pose any sort of hazard should there be any soot or creosote falling into that pit? and if so, what would be my options?