Iron Sun boxes are wired at 12 volts, which does not present an electrocution hazard. However, any electrical system can start a fire if connections are not done properly. It is important that all electrical connections, inside or outside the box, are done by a qualified electrician. Twisting wires together and covering them with electrical tape might work in the short term, but in the long term these amateur connections will fail, and might start a fire.
In regards to toxicity and off-gassing, nickel iron batteries are the safest battery you can buy. They are non-toxic, and off-gassing is not an issue with our small systems. The electrolyte, potassium hydroxide, is highly alkaline and can cause eye damage, but it is contained safely in the battery as long as the battery stays upright. Therefore it is important to keep the box upright to prevent spillage, and to keep children and pets from opening the box and playing with the wires or batteries, which can create a fire hazard. Put a strap and padlock around the box if this might be an issue.
Once a month, you will need to top off your battery with distilled water. This is a very safe process that does not put you in contact with the electrolyte.
Every 8-10 years, we recommend changing the electrolyte in your battery. Instructions on how to do this are provided with the Iron Sun kit, and are also available online. Care must be taken during this process to prevent eye damage from the corrosive chemical, and to prevent contamination of the electrolyte, which would impair the performance of your battery.