It we look logically at the ACOP L101 and apply the conditions for a confined space Regulation 1 tells us that a confined space is:
“any place, including any chamber, tank, vat, silo, pit, trench, pipe, sewer, flue, well or other similar space in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk”
So based on the above we now look at what they consider specified risk which is defined as means a risk of:
(a) serious injury to any person at work arising from a fire or explosion;
(b) without prejudice to paragraph (a) — (i) the loss of consciousness of any person at work arising from an increase in body temperature;
(ii) the loss of consciousness or asphyxiation of any person at work arising from gas, fume, vapour or the lack of oxygen;
(c) the drowning of any person at work arising from an increase in the level of liquid; or
(d) the asphyxiation of any person at work arising from a free flowing solid or the inability to reach a respirable environment due to entrapment by a free flowing solid
Regulation 1 Para 12 states
Under these Regulations a ‘confined space’ must have both of the following defining features:
(a) it must be a space which is substantially (though not always entirely) enclosed; and
(b) one or more of the specified risks must be present or reasonably foreseeable.
Now to be honest due to the ventilation rates in a typical spray booth it is unlikely anyone would become unconscious or be asphyxiated by the fumes and vapour although that doesn’t mean they are not exposed and can become ill.
To capture this occurrence Regulation 1 Para 14 & 15 captures this event and is what in my experiance a lot of companies refer to as a "Potential Confined space".
Regulation 1 Para 14: A place not usually considered to be a confined space may become one if there is a change in the conditions inside or a change in the degree of enclosure or confinement, which may occur intermittently. For example, an enclosed space may be free of contaminants and have a safe level of oxygen but the work to be carried out in it may change this, such as:
(a) welding that would consume some of the oxygen;
(b) a spray booth during paint spraying; or
(c) using chemicals for cleaning purposes which can add contaminants.
15 In such cases the space may be defined as a confined space while that work is ongoing and until the level of oxygen recovers or the contaminants have dispersed by ventilating the area.
The important word here is May which in legal speak “May” indicates possibility or permission, so there is a possibility that it could be considered as confined space, and you have permission should you wish to define it as such.
However, this is not the same as Should which suggests a recommendation or what is considered as the right thing to do e.g. in health and safety law arguments what is considered as the reasonable person argument.
So as there is a possibility that it could be a confined space you have permission to call and manage it as shuch should you wish to do so. However, it could be considered that a reasonable person would not managed or defined it as such in the eyes of the law.