Not so safe, but it all depends where you live in the city and all that. Downtown / midtown is the best, anything else is hit or miss. Areas on Moross St. by Grosse point are just as nice as anywhere else. Also, even though Detroit is arguably the most dangerous city in the country, suburbs are very safe.
Air conditioning tonnage has nothing to do with weight. A ton, as used in the HVAC field, is a term that describes how much heat the AC unit can remove from a home in one hour. The measurement for heat is the British thermal unit (BTU). One ton of air conditioning can remove 12,000 BTUs of air per hour. A four ton unit can move 48, 000 BTUs and so on. Therefore, the more tonnage an AC unit is rated at, the more air it can cool.
In the United States, the ton most commonly used is the short ton. In the United Kingdom, a tonne is a metric ton and is equal to 1,000 kilograms or 2,240 pounds. The term ton can also be used as a measurement of power. For example, in refrigeration, a ton is a unit of power.