Reports Dan Deakins...
Robbie Cundy saw red with just two minutes to go until the break for pulling down Rhys Murphy, who scored the subsequent penalty.
Despite threatening to score many more throughout the second half, the Clarets were blunt in front of goal, and had to hold off late pressure from Bath to prevent the equaliser.
Both sides were very evenly matched in the first third of the first half. There was very little rhythm to the game, with Chelmsford and Bath consistently breaking up the play in the midfield.
Ryan Brunt had the first clear chance for Bath in the 17th minute, turning in the box and shooting just wide of Nathan McDonald's far post.
Chelmsford got a chance of their own seven minutes later when Tom Wraight's throw found Max Porter but his shot was deflected out for a corner.
From Jai Reason's corner the ball made its way back to him on the edge of the Bath box. Reason cut inside and his curling effort was well saved by Bath goalkeeper Ryan Clarke.
Sean Rigg attempted a spectacular long range shot with 15 minutes of the half remaining, but it flew safely wide of Chelmsford's goal.
Wraight got in a few minutes later but his low cross was cleared far up field.
Chelmsford finally made the breakthrough two minutes before half time when Cundy pulled down Murphy inside the penalty area. The big centre half was sent off and Murphy stepped up, slotting the spot kick into the bottom corner to put the Clarets up 1-0 heading into half time.
10-man Bath hit the ground running in the early goings of the second half, with Adam Mann getting in behind and forcing a corner in the 49th minute.
Things almost got worse for Bath just five minutes into the second half, as Clarke took out Murphy on the edge of the box with the Chelmsford striker hurtling towards his goal. Referee Steven Hughes, rather controversially, only awarded a yellow card. Murphy's low effort from the freekick just outside the D went marginally wide, rippling the side netting.
Despite being at a mans disadvantage, Bath were playing very risky at the back, intent on building from the goalkeeper and Murphy very nearly stole the ball as Chelmsford pressed for a second.
Wraight nearly extended the lead in the 66th minute. The ball came to him on the left hand side of the box via Murphy and the winger's shot was blocked off the line by Mann.
Bath were close to a fortunate equaliser as the game approached the final 20 minutes: Joe Raynes' long throw-in bounced perilously close to McDonald's goal and it was cleared over the bar in the nick of time.
Andy Watkins went so close to equalising in the 77th minute, cutting a shot across the six-yard-box from a narrow angle and it ran just wide of the far post.
Substitute Scott Fenwick was guilty of a miss that will likely go down as one of the worst of the season. Murphy got in behind the defence in Bath's penalty area and squared for Fenwick, but somehow the striker put it past the near post from fewer than six yards.
Murphy again shot wide in the 83rd minute as the game became more and more nervy at 1-0 with Chelmsford unable to secure the win.
Wraight went from range with two minutes of normal time remaining but could only hit the netting supports.
Bath went straight up the other end and substitute John Mills almost converted a cross. The assist was far too powerful though and Mills was unable to guild the ball into the goal.
After a lot of late Bath pressure Chelmsford held on to win 1-0.