If you are able to 'absorb' chi from anywhere as you walk, then, do not do so while walking along polluted streets.
Chi works at the cellular level. Cell damage may occur if all these pollutants are fed into them constantly and at high levels.
Do what the ancients did -- find a quiet stream in a wooded area with large trees. Do your 'chi exchange' with these 'clean' trees.
"Pull" the energy from a group of large trees into your body and down to your soles as you breath in and 'return' it back to the trees as you breath out. Ten minutes will be enough. Best of course in the early morning when the oxygen level is high and clean.
Eyes shut or open as you wish.
Important to have happy positive thoughts.
After each session, clench your fists and notice the extra strength in them? Your body is already working at a higher level of efficiency.