Exploring the Acheron with a home build rebreather

Transporting and assembly of the rebreathers

Logistics for the rebreathers was something on its own. No high pressure gasses are allowed on airplanes. So a source of oxygen had to be found in Jamaica. Another problem was the absorber for the carbon dioxide. The scrubbers were build to contain 5.5 kg absorber each.  So we needed minimal 11 kg absorber. Even when this product would have been allowed on the plane, bringing all these extra kilos would have been costly. Luckily all these logistic nightmares were wonderfully handled by Jan for whom I'm very grateful.

The assembled rebreathers are rather bulky and couldn’t be put in the luggage like that. So the rebreathers where disassembled in loose parts and stowed away in the scrubber and in the counterlungs protective case. The frame itself was easily put in the luggage. The rebreathers where also disassembled because of the extra questions we could expect at the customs. To be honest when assembled they look like some sort of a doomsday machine.

Once we where in Jamaica each rebreather was assembled in less than 2 hours. They where tested by submerging in the swimming pool and pressurize them. Only one minor leak was detected at one of the mouthpieces which was easily fixed. Also the over pressure valves were tested like this and did their work well.

Carrying the rebreathers into St Clair

It's Wednesday 18 March 2009 and we are standing at the entrance of St Clair Cave. The walk to the cave was easier than last time. There is a new track which is a shortcut over a hill. This is a relieve in comparison with the old trail which followed the boulder covered dry Black River bedding. Today the team counts six people: Stef, Jan, Andrew, Douglas, Kurt and me. The goal is to carry both rebreathers and all the extra gear as far as possible into the St Clair Cave.

An oxygen sensor is calibrated at the entrance at 20.9 % oxygen. Then we descend into the cave with all our gear. In no time we are in the Junction Room at the entrance of the Inferno. To my surprise the oxygen level here is still 20.9 % at a temperature of 25 degrees Celsius. To enter the Inferno we have to wade through relative deep water. After the big rock, which guards the Inferno as a sentinel, the oxygen level starts to drop. The further we go into this gallery the more bats we see. There are thousands and thousands of bats hanging in thick packs at the ceiling. The sound of this massive amount of animals is more than impressive. From time to time we wade through hip high murky guano infested water with floating dead bats and everywhere we place our hands and feet there are the ever present cockroaches. Their number must be in the millions. The temperature rises more than six degrees Celsius while traversing this hell. When we reach the end of the Inferno the oxygen level has dropped to 15.6 %. So we can assume there is 5.3 % carbon dioxide in the air! And indeed we all feel the poisoning effects of the carbon dioxide. Our breathing is very rapid and carrying our load (for me this is a 17 kg rebreather, a bag with survey gear and a camera) is becoming a burden.

At the end of the Inferno we have to climb a perilous steep slope covered with a very thick layer of guano. This is followed by a 4 meter drop with muck covered rocks. The passage continues through a small horizontal crevice where at last a wider passage is reached, we are in the Inferno+. The rebreathers get some serious beating pulling and pushing them through these boulders. I hope they are still OK. Once in the Inferno+ I check the air again and read 14.4 % oxygen! This means there is more than 6.5 % carbon dioxide, too much to be good if you ask me. With a lot of effort and gasping after air we finally reach the entrance of the Limbo chamber. The oxygen level stays at 14.4 %.

This low oxygen level is a real setback for us. During the discovery of the Acheron in 2006 the air was breathable just into the entrance of the Acheron. Now the bad air begins much earlier and in fact contaminates the complete Inferno+! This means we will have to strap on our rebreathers much earlier than planed and we will have to crawl through some very restrictive passages in the Limbo before reaching the Acheron. I wonder how this is going to work...

But today it has been enough for us. We are all exhausted and really want to get out of this cave as fast as possible. We drop the rebreathers and other stuff on the slope leading to the Limbo and start our retreat out of this cave. Without the heavy load this goes easier than expected and we pass quickly through the boulders marking the passage between the Inferno and Inferno+. The further we get out of the Inferno the better the air gets and at last we are breathing normal air again. The heavy exhaustion we had in the Inferno+ is only a bad memory and after some Red Stripes we are ready for tomorrow to begin the exploration of the Acheron.

Exploring the Acheron with the rebreathers

Next day we go back to where we left the rebreathers. Today the team counts 5 people. Yesterday Douglas had to go back to Kingston. I mount the regulators on the rebreathers and do a thorough checkup, they seem to be OK.  To get into the Limbo an awkward climb has to be made. This can't be done with the rebreathers. So we climb without them into the Limbo and the rebreathers are hoisted up the ledge. Here we put the rebreathers on our back and open the oxygen valve. We set the oxygen flow to 1 liter/minute. The oxygen hisses and fills the counter lungs. Kurt and I put the mouthpieces in our mouths and breathe pure oxygen. We try to get through this chaotic chamber by following the left wall. But there are some very narrow passages between some huge rocks and as expected we soon are stuck and have to retreat. The rebreathers are too big! After careful consideration, Kurt and I decide to risk it and go through the small passages without the rebreathers and pull them through with the help of the others. Easier said than done but at last we are at the other side of these damned blocks and mount again our rebreathers. Here I want to say that Andrew was a real star. Without his help and courage we wouldn't have managed to pull the rebreathers through the Limbo. Thanks Andrew!

A last farewell to Andrew, and Kurt and I are on our own. The oxygen level in this place is 14 %. We leave the rocks behind and continue our journey downhill on a sandy slope. At last we reach the low Arch before the Acheron. The oxygen level here is only 11.1 %. Very strange but we still see some bats flying around. How they can sustain this foul air is a mystery to me.

We slip under the Arch and are entering the Acheron. At once the oxygen level tumbles to 7.9 %! Here we are standing in a natural sewer collecting the waste water of the Worthy Park sugar factory in Lluidas Vale. The composition of sewer gas includes: nitrogen, hydrogen sulfide, carbon dioxide, methane, ammonia, water vapor. No bats or cockroaches are seen. One thing is sure, one breath of this foul mixture and we are dead!

Afterthoughts

My first thought clambering out of this hell hole was never again! But since I've been fed well and drank enough Red Stripes the idea of going back is taking the upper hand again. Never say never again...

The rebreathers did work wonderfully well but need some rework. They are too oversized and to heavy. They should be scaled down and weigh maximum 13 kg. Also the way the internal oxygen sensor is mounted into the system should be more secure. They have the tendency to unscrew which is something which must be avoided at all cost. The manipulation of the oxygen regulator is also a point of concern. Sometimes we where so confused we didn't know anymore which way was open or close. Only when we heard the hissing becoming louder we knew we were turning the thing open.

The construction itself was caveproof. These rebreathers have been put through a very severe beating and nothing cracked or broke down. For which I am very glad.

I also want to express my deepest gratitude to all who has joined in this crazy endeavor. Thank you Stef, Jan, Andrew, Douglas and not the least my brother in crime Kurt. Without you guys it would have been impossible. Thanks!

I also have to thank Hilde and my daughters Lien and Tina for their patience with me. I know it’s not easy to live with a madman making rebreathers under one roof. Many thanks!