Atticus went through a whole series of tests attempting to assess the defensive capabilities of his suit.
He increased the temperature of the training room to staggering degrees. It was to an extent that Atticus wouldn't dare stay in such a space for a prolonged period of time before. He would have been melted like cheese.
But with him donning his suit, Atticus could proudly say that he didn't even feel any heat. The suit maintained the same exact temperature as before regardless of how much he turned up the heat.
Due to Atticus's incredibly keen senses, he was able to notice some slight changes in temperature anytime he abruptly increased the temperature. It only occurred for a second, but to Atticus, it was more than enough.
'It's as if the suit adapted,' Atticus immediately made some assumptions based on what he had observed.