During safety meeting onboard ship, chief mate said pipe tunnel is not an enclosed space as it has exist from forward and aft.

But to my understanding, I disagree with such, because may contain toxic gas, since bunker tank, ballast tanks and valves are all in connection. Provision of ventilation as he said, doesn't makes it a Sami enclosed space. Moreover, on tanker ships, ventilation is also provided in pump Room. Please share your opinions base on the topic.

Don't know your location in the world but here in UK the legal definition of "pipe tunnel " is as follows:-
"The void space running in the mid ships fore and aft lines between the inner bottom and shell plating forming a space for ballast, bilge and/or fuel lines"
I take it the mid ships statement is used as a reference point only.
Little bit confusing perhaps but you have to remember that court case outcomes for potentially millions of pounds are decided on the interpretation of the act and how they can be argued in a court of law.
So for me anyway the key words here might be " running in the midships fore and aft lines " which I take to be stood in the void amidships looking fore and aft.
So your chief mate has omitted the key word " in the midships " .
Bit confusing methinks perhaps.
Mr Warsila endorses this.
So I rest my case your honor.

From Canadian MOSH regulations the definition of an enclosed space is:
PART 1
General
Interpretation

confined space means an enclosed or partially enclosed space that

(a) is not designed or intended for human occupancy, except for the purpose of performing work;

(b) has restricted means of access and egress; and

(c) may become hazardous to any person entering it owing to

(i) its design, construction, location or atmosphere,

(ii) the materials or substances in it, or

(iii) any other conditions relating to it. (espace clos)

Part 14 covers specifics

https://laws-lois.justice.gc.ca/eng/reg ... index.html

I think, I'm right. I'm in UAE, same roles. But where he got the definition as a semi-enclosed space is what I don't know.

pipe tunnel aka duct keel, is definitely an enclosed space. Old cargo ship I worked on 35 years ago had one, had an entrance with a quick opening hatch at the focsle which led you down a vertical ladder to the belly of the ship. Exit was a bolted up hatch on the fwd ER bulkhead. Nest of piping for bunkering, tank ballasting, cargo bilge etc etc ran in there to/from the engine room. I was a 5th engineer and most of my time spent patching up (famous plastic steel putty and clamp fix) leaking bunker pipe (heavy oil) whenever we took bunker . I always exited/entered the keel via the engine room because I feared falling from the vertical ladder .

I would say that although the Pipe Tunnel Duct keel has access at both ends it would still be regarded as an enclosed space, because leaking fuel etc can fill the space with flammable / Toxic Gases and corrosion taking place could deplete the Oxygen levels.

However, if it is fitted with a supply fan at one end and an exhaust fan at the other and these are always kept running, to ensure that there is continuous mechanical ventilation of the spaces, then I would NOT regard it as an enclosed space. However, you need to know that the fans are running all the time and nobody is switching them off to save fuel or because they are noisy.

Big Pete

There is a lot of information re. enclosed spaces from SOLAS, IACS, Class, flag, MCA, PSC, P&I clubs and MAIB. There is so much information because we are still seeing a shocking number of fatalities, not only the initial victim but their rescuers as well. Personally, I consider it as an enclosed space because there isn't continuous ventilation, a possibility of 02 depletion and/or toxic gas. I have been in tunnels that were not classed as an ES but as the old saying goes: "Who is responsible for your safety? You are!" Admittedly, I am not aware of any incidents in pipe tunnels but I would have to convince myself that the space was safe to enter and would remain safe for the duration. Hopefully, we all have gas/02 meters on board so we can at least test the atmosphere at the ends, with portable fans blowing through. Entry should be made in port because we can't leave the hatches open at sea, ok, in the middle of nowhere in deep water there is not a big problem but if someone gets into trouble you have shore-side support. This job requires a full risk assessment. I am very well aware of just nipping down the tunnel for five minutes to check the position of a valve but this is just where you and your ship-mates get bitten. You need at least two people; one to go in and one at the door just like any other entry. When you go in take your meter and carry an ELSA set.
To experience the worst scenario, on your next enclosed entry and rescue drill, which you carry out every 1-3 months, try and get an unconscious person out of the middle of the tunnel in full BA kit. Can you even reach them in BA?