APCBack-UPS Pro 900 - UPS - 540 Watt - 900 VA

Always had APCs, but online / fully metallic older versions.So I wanted to protect my AV and purchased the 900VA unit - locally from authorized reseller.In the first month, the smell was not very easy to tolerate.In a big living room, you could sense from 3 meters away. Had to air the room frequently.Smell was something unclear like plastic, iodine and sulfur...?Plastics, circuitry, batteries? Hope not harmful.They told me from the shop that it 'll go away.And it did gradually after first month. Now, more than a year, you must be very close to smell something.But, yes there is a residual.Then, there is a constant buzz, when under normal operation with full batteries.Which slightly pitches up and down, probably due to the AVR circuity?In a big room you cannot hear, must go 1 meter close.But in a confined quiet office space, you could.APC support was really very accommodating.They told me noise is normal.But for the smell, they asked me if to replace last month. I was skeptical to do so, not wanting to have the smell issue from the start....I want another UPS now and I 'll try a different brand, with no AVR but better transfer time.