RE:Criteria for a halt?Fisher, from IIROC:
A stock is generally halted pending the release of material news that may affect the price of a stock. A trading halt allows the market to digest this information and also creates a level playing field among investors. Halts are issued by IIROC for regulatory reasons or at the request of the involved company. When a company requests a trading halt (usually prior to issuing a news release), the company must assure IIROC that its announcement is imminent. The nature of the announcement and the current status of events must also be disclosed to IIROC, so that IIROC can assess the need and timeframe for the trading halt. Halts can also be issued to restore fair and orderly trading.