Is it true a 1996 Chevy blazer does not have air bag sensors?

No, that's not entirely true. While the airbag system in a 1996 Chevy Blazer might be simpler than in later models, it does have sensors. It wouldn't deploy airbags without them. These sensors detect impact severity and trigger the deployment. However, the exact number and type of sensors might differ from modern vehicles. They likely have a primary impact sensor (often in the steering wheel or dash) and possibly others.