This study identifies communication design challenges associated with firefighters' personal protective equipment (PPE), an assemblage of wearable technologies that shield these workers from occupational hazards. Considering two components of modern firefighting PPE through Zuboff's (1998) theorization of information technology, we offer an extended case study that illustrates how these wearables, as interfaces, automate or informate firefighters' practice of safety. Often lauded for their abilities to augment firefighters' work capacities and increase safety outcomes, our analysis revealed that these wearables engender practices that expose firefighters to unforeseen hazards and displace the "tacit craft skills and knowledge" that these workers mobilize to mitigate workplace risk (Spinuzzi, 2005, p. 164). Drawing from these insights, we sketch four points of tension that communication designers, system architects, and practitioners may utilize to consider the informating potential of smart-firefighting PPE equipped with physiological sensors.