What do you think about when you hear the phrase “atmospheric testing”? If you are like most seafarers, the answer is probably oxygen, toxic and flammable gases. If these are within acceptable limits, you would think the conditions are safe for entry.
However, recent operational experience makes it clear you also need to account for carbon dioxide.
IMO’s revised recommendations for enclosed space entry encourage all maritime crews to update their routines. While oxygen levels may appear normal, dangerous amounts of carbon dioxide may be accumulating.
The most common way of doing atmospheric testing is checking the amount of oxygen, flammable and toxic gases in an enclosed space.
Previously, testing for CO2 has not been a focus for enclosed space entry. Residual cargo or biological activity may generate CO2 as a byproduct. CO2 may especially accumulate in rooms with limited air exchange. Gas stratification can occur, so it is necessary to test at several points.
Even if your oxygen readings appear normal, elevated CO2 levels may still be present.
Carbon dioxide is both colorless and odorless. It cannot be detected without appropriate instruments, though there are some warning signs.
Crew exposed to unsafe levels of CO2 might experience increased breathing rate, reduced concentration and impaired decision-making. The effects are subtle, so there is a risk of people remaining in a space while their performance is affected.
Strict measurement routines are important, as the impaired decision making actively works against the alertness required to notice that something is off.
In order to keep abreast of accumulating carbon dioxide, you should adopt some simple routines to ensure your enclosed spaces are safe for entry. Here is what this looks like in practice:
If your crew follows these guidelines, they may safely assume that the space is fine for regular operations.
To ensure your CO2 testing routines are not impaired, there are some technical issues to keep in mind.
Firstly, make sure your instruments are able to test for carbon dioxide at all. Only the GX-3R PRO and the GX-9000 can be configured to monitor CO2. Bruusgaard has updated recommendations to comply with Resolution MSC.581(110).
Secondly, watch out for sensor drift. Your instruments do not stay sharp forever, and must be calibrated regularly. Failure to do this may lead to a lower, delayed or even missing reading.
Finally, ensure you have a reliable supply of calibration gas. Shipments might be delayed or restricted due to DG (dangerous goods) logistics constraints. Do not wait until the last moment to resupply.
If all three issues are addressed, congratulations: Your routines are now up to date, and your crew’s well-being is ensured.