Signs of trouble include straining to breathe, or gasping for air, nervousness, increasing weakness culminating in collapse, dilated pupils, ashen grey or blue mucous membranes or bright red in cases involving carbon monoxide poisoning. I read somewhere that growing puppies are very susceptible to bone and joint injuries. A Provide secure footing for your Danny Boy, and keep him off slippery floors. Don't pick him up by his front legs, don't drop him, and don't encourage him to jump or walk on his hind legs. Keep an eye on his weight.
Obesity overtaxes growing bones and joints.
And call your vet at the first sign of any injury. My husband and I would really love to take Aphrodite with us. But we're traveling extensively by car this year and Affy gets carsick. A Talk to your vet about Aphrodite's problem with car sickness. In an extreme case, more serious medication may be called for.