On April 1, the Investment Industry Regulatory Organization of Canada (IIROC) published a notice relating to securities trading halts in coordination with the application of 'circuit breakers' on U.S. markets. In the U.S., trading halts occur based on trigger levels of 10%, 20% and 30% drops of the Dow Jones Industrial Average, calculated at the beginning of each quarter using the previous month's average closing value. The NYSE thresholds have been announced for the second quarter of 2010 as 1,050 points, 2,150 points and 3,200 points respectively.

It is IIROC's policy that it will coordinate trading halts with U.S. markets, but for days when Canadian markets are open and American markets are closed, IIROC has published related triggers based on drops in the S&P/TSX Composite Index. The TSX trigger levels are: Level 1 (10%) - 1,200 points; Level 2 (20%) - 2,400 points and Level 3 (30%) - 3,600 points, with the effects of the triggers depending on the time of day the threshold drop occurs. Triggering the Level 1 threshold between 2:00 and 2:30 p.m. results in a 30 minute halt in trading, while trading would be shut down for the rest of the day should a Level 3 halt occur.