I expect that the pool has a history of algae growth. Algae often forms itself in a circle, eating away the gunite underneath it.
indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes and businesses?
Failure to have good ventilation and bringing gaseous items indoors are the biggest causes of indoor air pollution. Some of the items that cause indoor air pollution include tobacco, pesticides, and asbestos.
No as long as the cement had gone of originally this is not a problem.
Around Christmas there can be many things, in some cases the tree could catch on fire, but in most cases its from forgetting the food inside the stove/oven.
I use a mixture of water and muratic acid, works well.
Rebar and or ties exposed in a gunite/shotcrete pool shell is bad but not unrepairable. The exposed steel can rust, and may bleed through the plaster leaving a stain. It may also cause the plaster to delaminate in that area. To remedy the situation the rebar and ties should be cut back or ground out and into the concrete. Hydraulic cement can be used to patch over the areas before the pool is plastered.
It is best if you do so that the water can circulate and so that the granular chlorine does not sit on a liner pool cause it will discolor the liner. With a gunite pool it can cause bleaching spots. It is not necessary though.
There are several negative effects of indoor plants. They can cause hay fever in some people, are very messy, and can be hard to keep alive due to limited sunlight.