Heat is not usually caused by bet spreads. That is, some floor usually doesn't look over and say 'wow, he's spreading 1 to 8, I'd better call surveillance!" However, much of the literature and many of the posts here advocate this idea. This is mostly Bullshit! Heat is usually a function of crossing a certain betting threshold. Some places they'll call "checks play" at $100, or $500, or table max, or $25 at fitzgerald's downtown. Whatever levels necessitates this call, may be their threshold at which they start watching. At some places, betting a certain denomination causes attention. Black action often does this. Spread 5-300 in green? Fine. Spread 10-100 with a black? The dealer starts screaming "Black action!" A smart surveillance crew may bust your ass for spreading a lot, but as long as you don't do anything that sets off their alarms, you're probably safe. That said, it's important to note that Vegas has a lot of sharp surveillance guys. So in Vegas, your spread may get you busted.