First responders are emergency response personnel who are usually the first people to arrive at the scene of an accident, incident, or crime. They can include police, fire, and EMT (emergency medical technicians) for more routine situations. More complex situations can require other personnel including hazmat teams (hazardous materials), bomb teams, and more specialized law enforcement (SWAT, FBI, etc.).
A first responder at the awareness level is a person who is trained to respond to incidents that involve hazardous materials. This can include toxic chemicals, radioactive materials, or explosive/flammable materials. A first responder to these types of situations must be able to assess exactly what materials are involved and what dangers they impose to people and the environment. This person must then be able to guide other first responders in how they deal with the situation. Basically they are there to make sure that a bad situation does not get worse and they do this by being very familiar with the particular dangers involved with different hazardous materials. As an example, some types of chemical fires are not quenched with water but are actually made worse if water is put on them. A first responder at the awareness level must be able to recognize this and guide fire personnel in the best way to put out the fire.
Many large businesses that deal with hazardous goods on their site often have one or more employees who are trained at the awareness level for just such emergencies.