A welder is preparing to enter a confined space. The atmospheric test results show an oxygen level of 18.5%, H2S at 15 ppm, and LEL at 0%. According to typical Canadian confined space regulations, what is the immediate consequence of these readings?

Question: A welder is preparing to enter a confined space. The atmospheric test results show an oxygen level of 18.5%, H2S at 15 ppm, and LEL at 0%. According to typical Canadian confined space regulations, what is the immediate consequence of these readings?

Answer options:

• Entry is permissible with continuous monitoring.
• Entry is permissible but only with supplied-air respiration. ✅ Entry is prohibited until atmospheric conditions are rectified.
• Entry is permissible, but a ventilation system must be activated immediately upon entry.

Correct answer: Entry is prohibited until atmospheric conditions are rectified.

Explanation: According to typical Canadian confined space regulations, the oxygen level must generally be between 19.5% and 23.5%, and H2S exposure limits (e.g., OEL of 10 ppm for an 8-hour TWA, or 15 ppm STEL) should not be exceeded. An oxygen level of 18.5% is too low, and 15 ppm H2S is above the acceptable continuous exposure limit, making entry prohibited until conditions are brought within safe limits.