Researchers in St. John’s are in their fourth and final phase of testing how immersion suits perform in cold water, wind and waves.
Tuesday was the last day of tests for a dozen volunteers who suited up twice for three hours at a stretch in the ice tank at the Institute for Ocean Technology (IOT) in St. John’s.
All that teeth-chattering is for a good cause: to help design better standards for testing immersion suits in real-life conditions.
Over the next few months, the data collected since Oct. 25 will be analyzed.
“It’s hard to draw any meaningful conclusions yet, but a lot of people have been getting out feeling cold,” said Jonathan Power, project manager with the National Research Council, which operates IOT.
“We’re trying to use our facilities to create more realistic environments to address a knowledge gap — the difference between the current calm water testing standards and more realistic conditions that people can find themselves in.”
The tank tests
A volunteer wearing an immersion suit is floating in a boxed-in section of the ice tank. He frequently flexes his hands.
During this round of tests, the water and air temperatures are cooled to 5 C. At the front of the box, a giant fan blows cool air over the volunteer.
Lise Petrie, human performance technologist with IOT, keeps an eye on the sensor readings on the laptop screens.
They track the volunteer’s core body temperature and heart rate using a pill-sized, wireless sensor swallowed by each participant. Petrie also monitors skin temperature at the extremities — fingers, face and big toes.
“If it gets too low, we pull them out,” she said.
Eight Celsius is too low.
From the front of the box, water is also pushed past the volunteer.
Researchers have found a person’s heat flow is affected by adding wind and wave conditions to the immersion suit tests. Heat flow is the amount of body heat lost to the environment. It can result in hypothermia.
Current standards for immersion suits require tests to be done in calm, circulating, 2 C water.
“While we’re using five degrees, this is a bit more taxing,” said Power.
The original plan was to carry out this round of tests in 2 C water and air temperatures, but Power said that was considered unsafe for the volunteers.
“If your extremity skin temperature drops below 8 C, you can actually get permanent damage.”
Rather than have a batch of three-hour tests that couldn’t be completed, researchers opted to keep the temperature at 5 C.
When each test is done, the volunteer heads for the hot tub to warm up.
Leaky suit project
On Tuesday, researchers also carried out a side project to test the effects of simulated leaks at the wrist and neck seals of the immersion suit.
In previous tests, volunteers were soaked with water before they put on their immersion suits.
To simulate a leaky suit, 1.55 litres of 5 C water is gradually pumped into the suit near the wrists and neck over three hours. Petrie monitors the effects.
During the first hour and a half, the volunteer’s core body temperature dropped slightly from the normal 37 C to 36.9 C.
The tests are also designed to measure how hard volunteers work to stay warm and prevent hypothermia.
“That’s where shivering comes into play,” said Power. “That’s why we have the mask on the participants — we’re measuring their oxygen consumption. And by measuring how much oxygen they consume we’ve got an idea of how much energy they’re expending to stay warm.”