<Tr> <Td> REL (Recommended) </Td> <Td> TWA 25 ppm (18 mg / m) ST 35 ppm (27 mg / m) </Td> </Tr> <Tr> <Td> IDLH (Immediate danger) </Td> <Td> 300 ppm </Td> </Tr> <Tr> <Th_colspan="2"> Related compounds </Th> </Tr> <Tr> <Td> Other cations </Td> <Td> Phosphine Arsine Stibine </Td> </Tr>

Where does ammonia play its most important role as a base buffer