The Hornets ended a four-game winless run with victory over Sunderland on Saturday afternoon and sit seven points clear of the relegation zone in 12th position, with only nine matches remaining.
Pulis said: "It will be a different game than the last two we've played but that's what the Premier League is about, coming up against different systems and different strengths".
"Until the table says mathematically we are safe, then we are not", the Italian manager told the club's official website.
Watford have scored a higher share of their Premier League goals in the opening 15 minutes of games than any other side (24%, eight of 34 goals); the second highest share is West Brom on 21% (8 of 39 goals).
Jose Mourinho labelled West Brom the best side in the league from dead-ball situations in the build-up to Saturday's goalless draw, and Watford were undone twice from set-pieces in their 3-1 defeat at The Hawthorns in December.
"We had a really good game against Sunderland and I was very, very happy", he added.
Jonny Evans and Chris Brunt scored first-half goals for the Baggies. We have to try to be careful not to concede any and, if we do, be careful from them. Christian Kabasele pulled one back for Watford, but a straight red card to Roberto Pereyra late scuttled any chances for a Hornets fight back. But he's a Watford player, and I'll show Watford respect.
"I might well decide who is going to play on Tuesday after the last session on Tuesday morning".
Troy Deeney has found the net in each of his last three Premier League games at Vicarage Road, equalling the record jointly held by Michael Ngonge in 1999, Heidar Helguson in 2000 and Odion Ighalo in 2015. "Weve offered him a contract and were hoping to get it sorted out", said Pulis.
Albion have been linked with a possible bid for the former Walsall forward ahead of their trip to Vicarage Road tomorrow night but Pulis played down any likelihood of the 28-year-old joining the Baggies this summer.
Matt Phillips is expected to miss the match with his ongoing hamstring problem, but Pulis may also be forced into a few more changes with the games coming thick and fast.