A hydrocarbon vapor detection instrument includes a hydrocarbon vapor detector, with conductivity proportional to contiguous airborne concentration of hydrocarbon vapor. The instrument further includes electronic circuitry providing an electrical signal proportional to the vapor detector conductivity and to a switch-selected sensitivity setting. The instrument further includes indicators to signal recharging status while a power switch is off and an external power supply is recharging the battery, namely that the battery is partially or fully charged and if the battery temperature is excessive, to signal that operating power is on, to signal that a low battery condition exists, and to signal different concentrations of hydrocarbon vapor. For the last of these, indicator position on a housing corresponds to vapor concentration. The instrument further includes an audible indication of power-on status and vapor concentration, changing with vapor concentration.