Agent-specific vaporizers minimize opportunities for error and evidence our specialty's commitment to patient safety as a general principle. End-tidal anesthetic gas concentration monitoring is a useful adjunct whenever inhaled anesthetics are used in operating rooms. Due to their expense and required maintenance, end-tidal anesthetic gas monitors are not commonly used in developing nations. Unfortunately, in resource-constrained environments, situations may arise in which inhaled anesthetic agent-vaporizer mismatch may be necessary in the absence of end-tidal anesthetic gas monitoring. Rather than merely censure such practice as a threat to safety, we believe that certain anesthetic agent-vaporizer mismatch situations can be safely managed providing patients with predictable inspired anesthetic gas concentrations while minimizing errors. We present an approach based on mathematical models and tested in an artificial lung model. Mismatching of inhaled agent and vaporizer is a dangerous practice and should not be performed unless it is absolutely necessary. Such situations may arise in remote locations where neither end-tidal anesthetic gas monitoring nor vaporizer-specific agent is available. We hope our article provides guidance in such situations.