My gas furnace ignites and blows hot air. After a few minutes the flame goes out but the blower continues blowing. Within a minute while the blower is still blowing, the gas reignites and the furnace runs for several minutes after this. This is not the usual way the furnace operates and it does not happen every time. Is this safe?

Hi emn and welcome, anytime a furnace malfunctions there's some danger. Make sure your filter is clean, vents are all open and that the flue is clear. If you post make and model your likely to get a better response. Good luck

If you are using one of those expensive "high efficiency" pleated air filters, take it out & try running the furnace. If that cures the problem, go get a cheap glass fiber filter.