Years ago, gasoline cans had a standard spout and a vent. Now due to environmental regulations in Pennsylvania, such spouts and cans are illegal to offer for sale in this state. Under the guidelines of the new law, gasoline containers must have a positive shut-off mechanism and vent only through the spout itself.
Ostensibly, this law was designed to lower the contribution of gasoline vapors into the air. It sounds like a great and environmentally responsible idea, doesn't it? The sad part of this regulation, is that when put into practice (as one might expect), many manufacturers simply satisfied the law in the lowest-cost way possible.
I grew up around cars, engines, lawn-mowers, and the like. I have a reasonable mechanical aptitude but as many times I've tried in earnest to use some of these new-style cans, I end up spilling more gasoline than ever*. I'm sure that many other people fumble in the same way I do and my guess is that the end-result of these 'green' containers is a notable and substantial increase in released hydrocarbon vapors.
I'm all for positive change -- even when it is scary -- yet the need for properly considered change goes well beyond the realm of gasoline containers. It seems when folks hurry too quickly towards new legislation, there is often a lack of forethought and more importantly a lack of prudent design which allows for a set of appropriate feedback and subsequent correction mechanisms.
*These spouts usually have a shutoff tip which diffuses the outflow tangentially instead of spilling it directly into the receiving tank. Often the tips are spring loaded and require substantial positive pressure against the tank opening but are so poorly designed that they slip off and cause an erratic flow into the tank. Also the spring will often jam allowing fuel to flow everywhere as you attempt to gracefully pull the rigid spout from the tank.