There are some main risks of using Nitrous Oxide in actual fact as fas as I know well still don't understand how it prodices the high and anethesia.
Two medically trained people have told me you need to breathe air after 1.5mins. After 2 minutes of no air (such as Nitrous) you will get hypoxia and brain cells will die. Since the buildup of CO2 carbon dioxide usually gives up the responce we need to breath in this is diverted by breathing in another gas like N2O or Helium. Basically advissable take large deap breaths of air befire having some N20 and for your first time set a stop watch going so you know when 1.5 minutes is up and you can turn off the tap or hold the bulloon tight.
More info seems to come forward all the time on the possible harms N20 does to the body. Thre is an Erowid article of an Aussie doctor who no longer uses it for aneathesia becuase he believed patioend recovered quicker and got less nastys likel pneumonia.
One of the worst relatively new theroies is that heavy use can damage use or even use in people with low Vitamin B12. Tingling, numbness in the extremeties or ringing in the ears for longer than a day could be the first signs of this painful condiftion, It can be permanent but also can be treated if treated earlier. Personally from my reading the standard Vitamin B12cyanocobalamin is crap it had to be processes through the liver into anything usable. The only bioalavlbe form I've read doctors say have a whole holst of other benefits including benefiting the eyes is vitaminB12 Methylcobalamin. You can find methylcobalamin on ebay, the talbets are small and if you read the label they are actually sublingual. Held under the tongue until filly dissolved to enter the blood their. 1 doctor was reccomendind 3000micrograms of methylcobalamin per day for suffering perople. My bottle says 1000mics a day for standard health.
I'm glad I've got onto this becuse I am vegetarian (usually low vB12) I've had just a box or two of ISI brand give me tingles, slight numbness in the forarms and finger tips.
Lastly if you've ever wiped out your dispenser after 4-6 boxes of ISI (Austraian) supposedly the best standard grafe bulbs if found it common the see black machine oil in my fingers and tiny flecks of metal.
I buy a pvc pipe jround the around the same diamater ad the mouthpiece (better the PVC a little small than way to big). You may wanna cut off those pointed bits off the plastic mouthpiece as they only pop bulloons and tear holes in filters. Next sew some kind of fairly thick cotton material around the mouthpice.. It could be a small baby sock ect, Now you cut lengths of the pvc pipe around 10cm or whatever you like. You need your N20 Dispenser with the mouthoice tughed oib tight and the fabric filter held (preferebly sewed on). Head one end of a piece of PCV pipe eith a heatgun, or if not available maybe a hot airdyer will do. A toaster definatley works just keep the pvc up and out of the toast slot. Once it's hot you can slife the hot end of the pvc pipe down only the mouthpice that already has the fabric filter. wait till really cool before pulling off.
When working you are only limited by your buloon size. for example get those big party balooonds roll in on the length of PVC the slide the other end of the pvc onto the mouthpiece. Crack a bulb into the machine and it done right you can hold down the handle without even holding the pvc pipe and buloon. Keep cracking more balloons and reasing ito the large baloon eash time. THe most I've put in one baloon so far is 7 and it just starts to look too big and silly to carry around.