Howell, who is seeking his first European Tour victory since 2006, sank five birdies to go six-under 207 for the tournament, one stroke ahead of George Coetzee.
Howell notch one of the birds on the par-3 16 when he dropped his tee shot within 3 feet of the cup.
Hansen, who last won on the tour in 2009, bogeyed the 16th and 17th holes for a round of 69.
Marcel Siem, the leader after two rounds, slopped to a 73 and fell into a fourth-place tie with Frenchman Raphael Jacquelin at 209.
Play was suspended for a short period Saturday due to rain moving through the Paris area.