Key points to cover
- A confined space is any enclosed or substantially enclosed space where there is a foreseeable risk of serious injury from hazardous conditions — it is defined by risk, not just size
- Never enter a confined space without a permit to work and a safe system of work
- Atmospheric testing must be carried out before entry and continuously during work
- A trained standby person must be stationed at the entry point at all times during work
- Emergency rescue arrangements must be in place before anyone enters
- Common hazards include toxic gas, oxygen depletion, oxygen enrichment, flammable atmospheres, flooding, and engulfment
Do's and don'ts
Do
- Ensure a valid confined space permit to work is in place before entry
- Test the atmosphere for oxygen, flammable gases, and toxic gases before and during work
- Keep a trained standby person at the entry point at all times
- Have rescue equipment (breathing apparatus, lifelines, harnesses) immediately available
- Ventilate the space mechanically where possible
Don't
- Never enter a confined space to rescue someone without following the emergency rescue plan
- Never assume a confined space is safe because it looks clean or has been entered before
- Never use petrol or diesel engines, or equipment that produces fumes, inside a confined space
- Never rely on smell to detect hazardous gases — many toxic gases are odourless
- Never remove or disable gas monitoring equipment during work
Questions to check understanding
Q1: What makes a space a 'confined space' under the regulations?
Show the answer
A confined space is any place that is substantially enclosed (though not always entirely) and where there is a reasonably foreseeable risk of serious injury from hazardous conditions such as toxic gas, lack of oxygen, flooding, or entrapment. Examples include manholes, tanks, silos, chambers, and deep excavations.
Q2: Why should you never rush in to rescue someone in a confined space?
Show the answer
Because the same hazard that incapacitated the first person (e.g. toxic gas or oxygen depletion) will likely affect the rescuer as well. HSE warns that people have died trying to rescue others from confined spaces. Always follow the pre-planned emergency rescue procedure.
Q3: What three gases should be tested for before confined space entry?
Show the answer
Oxygen (normal air is 20.9% and any significant change from normal is dangerous — check your gas monitor's alarm set points before entry, and if it alarms, get out and don't re-enter until the cause is found and put right), flammable gases (should be below 10% of the Lower Explosive Limit), and toxic gases such as hydrogen sulphide and carbon monoxide. Testing must be done with calibrated instruments before entry and continuously during work.
Q4: What should the standby person do if the worker inside becomes unresponsive?
Show the answer
Raise the alarm immediately using the agreed procedure, do NOT enter the space, attempt retrieval using the lifeline and harness from outside, and call the emergency services. The standby person's primary role is to summon help, not to enter the space themselves.
This is general guidance for UK construction sites. Check it against your own risk assessment, method statement and the site before you deliver it.