It appears you have some ceiling drywall missing, your fire-stop. And some rafters/ceiling joists, and insulation. Use straps every 4' of unsupported pipe, the rest will depend on the application, Figs. 18,19, 21,22;
http://www.fornobravo.com/PDF/duratech.pdf
With about 39" of pipe above the roof, some chimneys require that plate only on 18" and bigger pipe.... consult the fireplace manufacturer. Go on-line for their installation instructions.
I'll move you to HVAC for more responses..
Gary
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Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!