Circuit breaker

The three market-wide levels

• Level 1: S&P 500 down 7% from the prior close — 15-minute halt.
• Level 2: down 13% — another 15-minute halt.
• Level 3: down 20% — trading stops for the rest of the day.
• Levels 1 and 2 only halt the market before 3:25 p.m. ET; after that, only Level 3 applies.

Single-stock pauses

Individual US stocks have their own mechanism, Limit Up-Limit Down (LULD): if a stock moves outside a band around its average price over the previous five minutes, trading in that stock pauses for five minutes. Bands are 5% or 10% for most stocks during the day and wider near the open and close.

When they have fired

Market-wide breakers triggered four times in March 2020 (on the 9th, 12th, 16th and 18th). The current levels were set after the 2010 flash crash; the older rules had fired only once, in October 1997.

On BRVX

BRVX stock perpetuals are synthetic contracts quoted in USDT, and stock prices on BRVX move 24/7, including weekends, when the exchange itself is closed. A halt is a stock exchange rule, not a BRVX feature; on BRVX, risk on a stock position is set by leverage, capped at up to 50x on NVDA, and by the stop-loss you place.