Just keep a window open for a while for fresh air to circulate.
1	Just	just	ADV	RB	_	2	advmod	2:advmod	_
2	keep	keep	VERB	VB	Mood=Imp|VerbForm=Fin	0	root	0:root	_
3	a	a	DET	DT	Definite=Ind|PronType=Art	4	det	4:det	_
4	window	window	NOUN	NN	Number=Sing	2	obj	2:obj|5:nsubj:xsubj	_
5	open	open	ADJ	JJ	Degree=Pos	2	xcomp	2:xcomp	_
6	for	for	ADP	IN	_	8	case	8:case	_
7	a	a	DET	DT	Definite=Ind|PronType=Art	8	det	8:det	_
8	while	while	NOUN	NN	Number=Sing	2	obl	2:obl:for	_
9	for	for	SCONJ	IN	_	13	mark	13:mark	_
10	fresh	fresh	ADJ	JJ	Degree=Pos	11	amod	11:amod	_
11	air	air	NOUN	NN	Number=Sing	13	nsubj	13:nsubj	_
12	to	to	PART	TO	_	13	mark	13:mark	_
13	circulate	circulate	VERB	VB	VerbForm=Inf	2	advcl	2:advcl:to	SpaceAfter=No
14	.	.	PUNCT	.	_	2	punct	2:punct	_
