I have the Sportsta with techno gold filter and valves. Even during the summer (What there was of it in Tokyo this year) I wore mine on my 10 miles each way commute. It seems that Japan has the worst diesel emmisions standards in their vehicles and when you consider that nearly every other thing on the road is either a truck, bus, light truck, van or crane it makes for a real smelly mess.

If you regulate your breathing you can wear it for an hour (although Respro say its only for 30 min trips at XX litres of air per min)

I took an alternate route last week along a river so I didnt have to wear it but once I hit the traffic again it goes right on. One evening I had forgotten to let it dry out at work properly so didtnt wear it for about 7k's. Man! What a difference it makes. I couldnt wait to get to the river. Anyone who commutes and dosent wear a mask is nuts IMHO

Top and bottom, 07:30~08:30 rush hour traffic on main roads. No black boogers, teeth or coughing once you stop. The filters are not too cheap but its gotta be worth whatever they cost (About $1 per week)

Simon