Finding Multiple peaks, and duration of peaks

I believe there are many different strategies and algorithms for processing these kind of signals, and I am far from an expert in the field. You might spend some time researching "signal processing" and "signal processing in excel" or similar search terms to get a feel for the information that is available.

Easiest approach might be a simple "when is signal above a threshold" value. This kind of approach might look something like:

1) Choose threshold (0.1 or 0.05 or whatever you deem appropriate).
2) Identify points that are above the threshold value. In Excel, this could be as simple as =$B2>D$1 (if threshold is entered into D1). then copy down. This will yield a column of TRUE/FALSE values. TRUE values mark the peaks.
3) To identify start and end of peak, you would then analyze this column looking for the points where column D changes from FALSE to TRUE (marks start of peak) and where D changes from TRUE to FALSE (marks end of peak). This could be as simple as =D3=D2 (maybe entered in E3) then copy down. Most results in this column will be TRUE, with the occasional FALSE value marking the start and end of peaks.
4) To aid in searching for start and end of peak values, a "counting column" could be added that counts the FALSE values in column E. =IF(E3,F2,F2+1) will increment for each FALSE value, giving a column of 0, 1, 2, 3, 4, ....
5) An INDEX(column A, MATCH()) combination could then be used to find the start and end of peaks in column F and return the corresponding time from column A. These could then be used to find duration of peak.

Let us know if you need specific help with any of these steps.