Abstract: There is a growing call for the use of open source content standards for all-hazards, all-media alert and notification systems. This paper presents findings on the implementation of Common Alerting Protocol (CAP) as a content standard for a community-based hazard information network in Sri Lanka. CAP is being deployed as part of the HazInfo project, which has established last-mile networking capability for 32 tsunami-affected villages in Sri Lanka in order to study the suitability of various Information Communication Technologies (ICTs) for a standards-based community hazard information system. Results to date suggest that the basic internetworking arrangement at lower technical layers has proven to be reasonably robust and reliable but that a key challenge remains in the upper layers of application software and content provision. This is evident in the apparent difficulties faced when implementing CAP messaging over multiple last-mile systems that include commercial satellite and terrestrial network technologies (C/L/X-Band, GSM, and CDMA in modes of voice and text). Lessons learned from silent tests and live exercises point to several key bottlenecks in the system where the integrity of CAP messages is compromised due to problems associated with software interoperability or direct human intervention. The wider implication of this finding is that content standards by themselves are not sufficient to support appropriate and timely emergency response activities. Those working with content standards for hazard information systems must consider closely the interoperability issues at various layers of interconnectivity.