Yes. The danger to you is a battery explosion. Batteries contain hydrogen gas, which can ignite and explode if a spark occurs anywhere near the battery. Batteries also contain acid which may be splashed on you if the battery explodes.
The danger to your vehicle is if someone reverses the jumper connections or touches the jumper cables together. The voltage surge that results may damage your charging system and/or other electronic components in your vehicle. To minimize these risks, use the following procedure when jump : Do not smoke. You should also wear eye protection. Make sure the vehicles are not touching (contact could provide an unwanted electrical path). Turn your engine off. Connect the red jumper cable from the positive (+) post or terminal on your "good" battery to the positive post or terminal on the low or dead battery in the other vehicle. Connect the black jumper cable from the negative (-) post or terminal on your good battery to a solid ground on the other vehicle. CAUTION: DO NOT make the final jumper connection directly to the low or dead battery itself. The reason for not doing this is because the final jumper connection usually produces a spark. Making the final connection away from the battery will minimize any danger of an explosion by keeping the spark well away from the battery. Make sure the ground connection on the vehicle with the low or dead battery provides a good electrical contact. Use an unpainted metal surface like an engine bracket or a frame member. Make sure the cables do not touch each other and that the cables are clear of the fan and pulleys on both vehicles. Start the engine in the vehicle with the good battery. Run the engine at fast idle for several minutes before attempting to start the vehicle with the low or dead battery. This will allow the charging system to pump some life into the other battery lessening the drain on the good battery and charging system. As soon as the vehicle with the dead battery starts, disconnect the battery cables. The vehicle should then be run or driven at least thirty minutes to recharge the low or dead battery. Additional charging time may be required depending on the battery's condition and state of charge. If the vehicle does not crank or cranks slowly, recheck the jumper connections. If it still doesn't crank, the problem may be something other then the battery (such as a bad starter, solenoid, battery cable connection or internal engine problem). If the vehicle cranks normally, but refuses to start, it may have an ignition, fuel or mechanical problem. Do not crank the starter more than thirty seconds at a stretch. Allow the starter to cool for about two minutes before cranking the engine again. Continuous grinding of the starter can cause it to overheat and fail. Continuous cranking can also sap the juice out of your good battery and/or overload and possibly damage your charging system, too!
