Listing requirements vary from one exchange to the next.
On the New York Stock Exchange (NYSE), if a security’s price closes below $1.00 for 30 consecutive trading days, that exchange would initiate the delisting process.
If a ticker the letters “BC” attached indicate the stock is non-compliant. But such companies may continue trading normally on the exchange during their probationary periods. Probationary periods are the time they have to become compliant with the rules.