What's a "confined space"?

I recently received the following query regarding the application of the Confined Space Regulations 1997:

“is the intent that any room that has a hazard in it is considered a Confined Space? Let’s say we have a room with 2 doors, some general dilution and exhaust ventilation, and has a CO2 line running through it with several flanged connections. The line has never leaked, but I suppose it could if something breaks. Is that a confined space according to the regs?”

The term “confined space” has a particular legal meaning. Once a space is defined as such then the requirements of the “Confined Spaces Regulations 1997″ become applicable and employers are required to

• avoid work in the confined space “as far as reasonably practicable”
• where work is necessary, ensure that there is a safe system of work
• make arrangements to safely rescue anyone who becomes incapacitated within the confined space.

It isn’t true that any room containing a hazard would be considered as a “confined space”. However, I would probably categorise the situation described in the query as such. I once had to deal with a similar situation – a pub cellar where there are CO2 cylinders. There was a risk of a cylinder “bursting” which could release gas into the room. HSE does include “unventilated or poorly ventilated rooms” as an example of a confined space in their guidance on the Regulations in their guidance leaflet, indg258 .

Our British approach is a little woolly, but allows flexibility. The crucial questions to answer when deciding on whether something is a “confined space” are

1. Is the room “substantially” enclosed? i.e. is access / egress limited?
2. Is a potential hazard present in the room ( or one is “reasonably foreseeable”)?
3. In the case of a hazardous gas/vapour/fume/dust, is ventilation limited so that a dangerous concentration is possible?

If the answer to each of these is “yes”, particularly if access/egress limited, then I’d classify it as a confined space and the Confined Spaces Regulations would apply.

In the example given in the query, it appears that there is limited access/egress and there is a reasonably foreseeable risk (albeit small) of a leak. If the concentration could build up to a dangerous level than I’d definitely classify it as a confined space under the Regulations. So the crucial test is whether a leak would lead to a dangerous concentration.

Detailed guidance on the Regulations are available here