You might check with a safety expert on working for prolonged periods under
old houses, especially for the proper respirator to keep your lungs free from
mold, bacteria, dust, and toxic particles. Old houses accumulate fertilizers,
poisons, chemical compounds, and other unhealthy substances that literally fall
through the floorboards. Animals leave waste and algae has a field day. The
suggestion for forced air ventilation is a good one. Lighting should be cold,
as hot lamps could ignite dust and trigger unwanted fire. I suggest vaccuuming
the soft soil along your path first, setting up a sled to move equipment and
pass buckets, then install safety lights and equipment. I once dug 3 meters
into a fill and had to install pumps to keep water from flooding the hot, dank,
and generally miserable working conditions... and my crew came down with fungus
infections that were no fun. Heck, even a hookah breather rig might be in
order for prolonged work under the building.

Ron May
Legacy 106, Inc.