Safety Basics · Lesson 10 of 14

Confined space awareness

What a confined space is, and why you never go in uninvited.

Please read: this free course is general education only. It is not a certification, it does not replace your employer's site-specific training, and it does not give you Working at Heights, WHMIS, First Aid or any other ticket — see the safety tickets guide.

Updated: Oct 2026.

A confined space is generally a fully or partly enclosed space that isn't designed or intended for people to work in continuously, and has a limited or restricted way in or out that can make first aid, rescue or evacuation difficult. Exact legal definitions vary by jurisdiction.

Why confined spaces are so dangerous

  • The air inside can lack oxygen or contain toxic or flammable gases.
  • Escape and rescue are harder because of the tight entrance and layout.
  • Many workers are injured and killed in confined spaces each year, and an estimated 60% of the deaths have been would-be rescuers.

The basics of safe entry

  • All confined spaces should be treated as hazardous unless a competent person has determined otherwise.
  • Before entry, a trained and experienced person identifies and evaluates the hazards.
  • The air is tested from outside the space before entry, side to side and top to bottom. Continuous monitoring may be needed.
  • Ventilation and other controls are put in place, and test results are recorded on an entry permit.
Never enter, and never go in after someone, unless you've been trained and the entry is authorized under your employer's confined space program. Raise the alarm and call for trained rescue.

This lesson is awareness only. Confined space entry needs specific training under your jurisdiction's rules; see the tickets guide.

Key takeaways

  • Confined spaces have restricted entry and exit and may have deadly air.
  • An estimated 60% of confined space deaths have been would-be rescuers.
  • Air must be tested from outside before entry; entry is controlled by permit.
  • Never enter without training and authorization.

Check yourself

A quick self-check. Your answers stay in your browser: nothing is saved or sent anywhere, and it isn't a test for a certificate.

1. A co-worker collapses inside a tank. What should you do?
2. When should the air in a confined space be tested?
3. How should you treat a confined space that hasn't been assessed?

Sources

  1. CCOHS — Confined space: introduction (opens in a new tab)